Ingenious hardwood

Manual for design and structural

3rd revised editioncalculation in accordance with Eurocode 5

BauBuche Beech laminated veneer lumber

Hans Joachim Blass, Johannes Streib

This manual provides clear design assistance to the user when handling the

new material “Laminated veneer lumber made from beech”. Relevant principles

and regulations from Eurocode 5 are presented and explained in more detail to

facilitate the design of members made of Beech laminated veneer lumber.

Prac tical design examples should also make it easier for engineers to apply

these regulations.

Please note that this manual does not constitute a replacement for design codes

and approvals. When using the design regulations specified in this work, com­

pliance with current calculation standards must be verified at all times. In addi­

tion, the strength and stiffness values specified here for Beech laminated veneer

lumber (Board BauBuche S / Q) and glulam made from Beech laminated veneer

lumber (Beam BauBuche GL75) must always be compared with the values from

the current approval / ETA or or the declaration of performance of the products used.

This design assistance is based on Eurocode 5 (DIN EN 1995­1:2010­12).

German national regulations will subsequently be listed in the relevant sections

and iden tified by shading in grey.

Moreover, they prevail in all cases over the regulations of the main part of

Eurocode 5. The numbering of the formulas is based on the system used in Euro­

code 5 or that of the National Annex, additional formulas are not numbered.

The usage examples and tabular design aids use strength and stiffness values for

BauBuche in accordance with current performance declarations (PM­005­2018,

PM­008­2018) or the European Technical Assessment ETA­14/0354 as of 11.07.2018.

We would like to thank the office of merz kley partner ZT GmbH for making

suggestions and reviewing the 1st edition of the manual.

Karlsruhe, September 2019

Hans Joachim Blass, Johannes Streib

Ingenious hardwood

Manual for design and structural calculation in accordance with Eurocode 5

BauBuche Beech laminated veneer lumber

Hans Joachim Blass, Johannes Streib

5

1 Product line

1.1 Board BauBuche

1.2 Beam BauBuche GL75

2 Principles of calculation and construction

2.1 Load­duration classes

2.2 Service class

2.3 Modification of the material properties

2.4 Verification in accordance with the partial factor method

2.5 Summary

3 Material properties

3.1 Strength properties for the Board BauBuche S and Q

3.2 Strength properties for Beam BauBuche GL75

3.3 Shrinking and swelling

3.4 Specific weights to calculate the dead load

3.5 Corrosiveness

4 Ultimate limit state

4.1 Verifications

4.2 Stability of members

4.3 Beams with variable cross­sections

4.4 Notched members

4.5 Step joints

5 Serviceability limit state

5.1 General points

5.2 Deflections

5.3 Vibrations

6 Connections with dowel­type metallic fasteners

6.1 Load­carrying capacity of connections with laterally loaded fasteners

6.2 Nailed connections

6.3 Stapled connections

6.4 Bolted and dowelled connections

6.5 Screwed connections

7 Glued components

8 Shear walls and diaphragms

8.1 General

8.2 Shear walls

9 Reinforcements and rehabilitation

9.1 Reinforcements for tensile stresses perpendicular to grain

9.2 Types of reinforcement

9.3 Applications

9.4 Cross­sectional reinforcements

9.5 Reinforced connection

10 Structural fire design

10.1 General

10.2 Requirements

10.3 Strength values

10.4 Actions

10.5 Design method

10.6 Charring

10.7 Connections with timber side members

11 References

12 Application examples

page

6

7

9

13

23

28

43

47

48

60

64

66

CONTENTS

6

1.1 Board BauBuche

The process of manufacturing BauBuche as lami­

nated veneer lumber panels involves beech wood

veneers being bonded together. In the process,

the veneers can either be bonded all parallel to

the grain in the main load­bearing direction (Board

BauBuche S) or with up to 30 % cross veneers

(Board BauBuche Q). The Board BauBuche Q has

superior dimensional stability when exposed to

changing climatic conditions as well as being

better able to resist in­plane tensile stresses

per pendicular to the grain. However, the arrange­

ment of cross veneers means a reduction in

bending strength as well as compressive and

t ensile strength parallel to the grain. The Board

BauBuche S is thus suited for forming linear

members, while Board BauBuche Q is primarily

for plates (e. g. wall panels).

The term veneers refers to sheets of wood around

3 mm thick, which are extracted in the form

of rotary peeled sections from beech trunks.

By gluing together the chamfered ends veneers

of virtually unlimited length can be manufactured.

This approach also allows damaged areas to be

cut out. The reduced thickness of veneers makes

it easier to use the beech wood in a cost­effective

manner. This approach also minimises both the

time and thus cost involved in drying the wood.

In accordance with the current declaration of

performance, Boards BauBuche can be manufac­

tured up to a length of 35 m, a width of 1.85 m

and thicknesses ranging from 21 to 66 mm. The

deliverable panel dimensions must be confirmed

with the manufacturer before planning.

1.2 Beam BauBuche GL75

The manufacture of the glulam Beam BauBuche

GL75 involves gluing together at least two lamina­

tions made of Board BauBuche S with a thickness

of 40 mm or 50 mm. Beam BauBuche GL75 may

be manufactured with widths between 50 and

300 mm, heights between 80 and 1360 mm and

lengths of up to 18 m. A maximum precamber

of the Beam BuBuche GL75 of up to L/100, larger

dimensions (a height of up to 2500 mm, a width

of up to 600 mm and a length of up to 36 m) as

well as block glued glulam are regulated in the

assessment documents, but should be confirmed

with the manufacturer prior to planning.

Figure 1: Products made of beech LVL:

Board BauBuche S and Q; Beam BauBuche S; Beam BauBuche GL75 and BauBuche Panel

1. PRODUCT LINE

7

2.1 Load­duration classes

The strength of timber declines with increasing

duration of load. Accordingly, the loads exerted

are categorised into various load­duration classes

(KLED). The classification is based on the accu­

mulated load duration, referencing the service

life of the construction. A total of five load­dura­

tion classes are distinguished. Loads from the

dead weight are defined as load­duration class

“permanent”. Variable loads are classified in stag­

es in the load­duration classes as “long­term”

(e. g. stored goods), “medium­term” (e. g. live

loads in living spaces), “short­term” (e. g. snow)

and “instant a neous” (e. g. earthquake). More

examples are included in Table NA.1. In cases

in which no clear allocation is possible, the clas­

sification should be made by consulting jointly

with the architect and building owner.

2.2 Service class

The level of humidity has a key impact on the me­

chanical strength and creep behaviour of wood,

which is why it has to be taken into consideration

when designing wooden members. Based on the

expected climatic conditions to which the mem­

ber will be exposed throughout its period of use,

classification is made into one of three service

classes. The use of load­bearing members made of

BauBuche is only permissible in service classes 1

and 2. There is no need to differentiate the me­

chanical strength properties of BauBuche within

service classes 1 and 2. In the event of BauBuche

being securely used in service class 1, the charac­

teristic compressive strength may be increased

(cf. Chap. 3.1.2). Conversely, the higher level of

creep behaviour of BauBuche in service class 2

compared to service class 1 must be taken into

account.

Service classes 1 is defined as an ambient climate

with a temperature of 20 °C and relative humidity

below 65 %. Members in closed or air­conditioned

buildings are generally allocated to service class 1.

In service class 1 the average wood moisture con­

tent tends to be less than 12 %.

Service class 2 is defined as an ambient climate

with a temperature of 20 °C and relative humidity

of up to 85 %. This applies to members in build­

ings which cannot be air­conditioned (not

enclosed on all sides) but which are protected

against weathering. Under certain circumstances

and based on the planned usage, it may also be

necessary to classify closed buildings in service

class 2 (e. g. greenhouses). In service class 2

the average wood moisture content tends to be

less than 20 %.

The fact that any adjustment of the level of wood

moisture content in line with the ambient climate

is delayed due to the slow rate of moisture trans­

fer means the relative humidity may exceed the

values specified above for a few weeks in a year.

2.3 Modification of the material properties

2.3.1 Strength

Depending on the load­duration class, the charac­

teristic strengths should be adapted with the modifi­

cation factors kmod in accordance with Table 1. When

connecting members with differing time­ dependent

behaviour, for kmod the square­root of the product

of the individual kmod values is to be used.

kmod = kmod,1 · kmod,2 (2.6)

If the load exerted by the exposures of various

load­duration classes is collectively applied,

the impact of the shortest load­duration classes

should be used to determine kmod . However, there

is always a need to check whether the load case

“permanent loads” is governing the design.

2.3.2 Creep behaviour

In structures made of members with different

creep behaviour, the final values of the mean

moduli of elasticity, shear or slip moduli must

be used to calculate the final deformations. For

this purpose, the mean values are divided by the

factor (1 + kdef ). The values for the deformation

factor kdef are taken from Table 1 depending on

the service class.

If the internal forces or moments also depend on

the individual stiffness values (when calculating

in accordance with second order theory), the

mean moduli of elasticity, shear or slip moduli

should be divided by the factor (1 + ψ2 · kdef ).

2 PRINCIPLES OF CALCULATION AND CONSTRUCTION

DIN EN 1995­1­1, Chap. 2

8

For connections between members with the same

time­dependent behaviour, kdef must be doubled.

For connections between members with differing

time­dependent behaviour, kdef amounts to

kdef = 2 · kdef,1 · kdef,2 (2.13)

2.4 Verification in accordance with the partial

factor method

To verify the members and connections, the actions

FE are compared with the resistances FR. The

goal is to minimise the probability of any failure,

namely an incident where the effect of actions

exceeds the resistances, without rendering the

cost of construction unfeasible. For this purpose,

the partial factor method multiplies the actions

FE with the partial factors γ in accordance with

Table 2 and divides the resistances FR by the

partial factor γM for a material property and

multiplies it by the modification factor kmod.

For BauBuche, the value to be used for ongoing

and temporary design situation is γM = 1.2,

but in the event of an accidental design situation

(e. g. fire) γM = 1.0 may be used.

For the persistent and transient design situation,

γM = 1.3 can be used.

Note: For the following examples, γM = 1.3 is

used in accordance with the national annex for

Germany.

Table 1: Modification factor kmod and deformation

factor kdef for BauBuche

FRkFRd = kmod · ――― (2.17)

γM

Both the actions FE as well as the resistances FR

are generally distribution functions of random

variables. The reliability can be further enhanced,

whereby instead of the mean values of these

random variables, upper (E) and lower (R) quantile

values are used for the purpose of design. For

resistances, the 5th­percentile is generally used.

Table 2: Partial factors coefficients for the ultimate

limit state, * Recommendation

2.5 Summary

Table 3 and Table 4 provide an overview of the

stiffness values at the serviceability limit state

(SLS) and the ultimate limit state (ULS). When

performing verifications of entire systems, mean

stiffness values can be assumed, since members

with lower stiffness properties within a system

are offset by their more rigid peers.

The 5th­percentile for the stiffness of connections

may be determined by reducing the mean value

Kmean via the ratio E0,05 / Emean .

Permanent Variable

actions actions

Unfavourable

effect γG,sup = 1.35 γQ = 1.50

Favourable

effect γG,inf = 0.90* –

Table 4: Stiffness values for individual members

SLS ULS

t = 0 t = ∞

E0,05 E0,05Members Emean ――――― ――――――――

γM γM · (1 + kdef)

G0,05 G0,05 Gmean ――――― ――――――――

γM γM · (1 + kdef)

Con­ 2 · Kser · E0,05 2 · Kser · E0,05nections Kmean ―――――――― ―――――――――――――――

3 · γM · Emean 3 · γM · (1 + kdef) · Emean

Table 3: Stiffness values for systems

SLS ULS

t = 0 t = ∞

Emean EmeanMembers Emean ――――― ――――――――

γM γM · (1 + kdef)

Gmean Gmean Gmean ――――― ――――――――

γM γM · (1 + kdef)

Con­ 2 · Kser 2 · Ksernections Kmean ――――― ―――――――――――

3 · γM 3 · γM · (1 + kdef)

kmod kdef

Class of the load duration

continuous long medium short very short

1 0.60 0.70 0.80 0.90 1.10 0.60

2 0.60 0.70 0.80 0.90 1.10 0.80

service

class

9

fm,k

Bending strength parallel to the

grain direction of the top layer

fm,90,k

Bending strength perpen­

dicular to the grain direction

of the top layer

ft,0,k

Tensile strength parallel

to the grain direction of the

top layer

ft,90,edge,k

Tensile strength perpendicular

to the grain direction of the

top layer in the panel plane

fc,0,k

Compressive strength parallel

to the grain direction of the

top layer

fc,90,edge,k

Compressive strength perpen­

dicular to the grain direction of

the top layer in the panel plane

fc,90,flat,k

Compressive strength perpen­

dicular to the grain direction of

the top layer and perpendicular

to the panel plane

fv,k

Shear strength

fvR,k

Rolling shear strength

Edgewise Flatwise3.1 Strength properties for the Board BauBuche

S and Q

When designing the Board BauBuche, it is impor­

tant to take into account the direction of the

loading and the orientation of the cross­section

precisely. For this reason, e. g. the values for

compressive strength perpendicular to the grain

fc,90,k differ depending on whether loading of the

wide or narrow surface is involved. The following

considerations are based on the “German general

construction technique permit (Allgemeine Bau­

artgenehmigung)” no. Z­9.1­838 as of 19.09.2018

and the performance declaration PM­005­2018 as

of 27.07.2018.

3.1.1 Bending strength

The characteristic value of the bending strength

fm,k is to be reduced for members of height h

between 300 mm and 1,000 mm with the coeffi­

cient kh. Members with h larger than 1,000 mm

currently must not be subject to bending stress.

300 0.12kh = ――― (3.3)

h

3.1.2 Compressive strength

The values for compressive strengths fc,0,k and

fc,90,k show a significant negative correlation with

the wood moisture content. Provided the classifi­

cation of the member in service class 1 is ensured,

the compressive strengths may, in accordance

with the details of Tables 8 to 11, be increased with

a factor of 1.2.

3 MATERIAL PROPERTIES

The strength values must be taken from the current approval / ETA

or declarations of performance for BauBuche.

The strength values depend on the angle between the load and

fibre direction and the member geometry.

Table 5: Definition of the

strength designations

for BauBuche

Table 6: Coefficient kh

Member height

in mm kh

300 1.000

400 0.966

500 0.941

600 0.920

700 0.903

800 0.889

900 0.876

1,000 0.865

10

Characteristic strength values in N/mm2

Bending fm,0,k *) 70.0

fm,90,k *) 32.0

Tension ft,0,k (39.7) – 46.0b) – (50.6) (39.7) – 46.0b) – (50.6)

ft,90,edge,k 15.0 15.0

Compression fc,0,k 57c) – (68.4) 57c) – (68.4)

fc,90,edge,k 40.0c) – (48.0) 40.0c) – (48.0) 40.0c) – (48.0)

fc,90,flat,k 16.0c) – (19.2) 16.0c) – (19.2)

Shear fv,k 7.8 7.8 3.8

Rolling shear fvR,k 3.8

Stiffness values in N/mm2

Modulus of E0,mean 11,800 11,800

elasticity E0,05 10,900 10,900

E90,edge,mean 3,500 3,500

E90,edge,05 3,200 3,200

E90,flat,mean 470 470

E90,flat,05 400 400

Shear Gmean 820 820 430 430

modulus G05 540 540 360 360

Density values in kg/m3

ρk 730

ρmean 800

Table 9: Characteristic values

for Board BauBuche Q

where nominal thickness

B ≤ 24 mm *) in N/mm2

3.1.3 Tensile strength

The characteristic value of the tensile strength

ft,0,k parallel to the grain is based on a length

of 3,000 mm. For larger or smaller lengths, the

coefficient kℓ shall be used.

Characteristic strength values in N/mm2

Bending fm,k (64.9) ­ 75.0a) 80.0

Tension ft,0,k (51.7) – 60.0b) – (66.0)

ft,90,edge,k 1.5

Compression fc,0,k 57.5c) – (69.0)

fc,90,edge,k (11.7)c) – 14.0

fc,90,flat,k 10.0c) – (12.0)

Shear fv,k 8.0

Stiffness values in N/mm2

Modulus of E0,mean 16,800

elasticity E0,05 14,900

E90,mean 470

E90,05 400

Shear Gmean 760 850

modulus G05 630 760

Density values in kg/m3

ρk 730

ρmean 800

Table 8: Characteristic values

for Board BauBuche S with

a nominal thickness

of 21 to 66 mm in N/mm2

3,000 s/2kℓ =min ――――― where s = 0.12 (3.4)

ℓ

1.1

Member length

in mm kℓ

500 1.100

1,000 1.068

2,000 1.025

3,000 1.000

4,000 0.983

5,000 0.970

6,000 0.959

7,000 0.950

8,000 0.943

9,000 0.936

10,000 0.930

20,000 0.892

35,000 0.863

Table 7:

Coefficient kℓ

*) Board BauBuche Q with a nominal thickness

of B ≤ 24 mm must not be used in edgewise

bendinga) for 300 mm < h ≤ 1,000 mm fm,k is to be

reduced by kh = (300/h)0.12

b) f t,0,k is to be multiplied by kℓ = min

{(3,000/ℓ)s/2; 1.1} where s = 0.12c) fc,0,k, fc,90,edge,k and fc,90,flat,k in service class 1

may be multiplied with the factor 1.2d) fm,k may be multiplied by kh,m = (600/h)0.10

e) ft,0,k may be multiplied by kh,t = (600/h)0.10;

where h is the longer side lengthf) fc,0,k and fc,90,k may be multiplied in service

class 1 by the factor 1.2g) fc,0,k may be multiplied by kc.0 = min

(0.0009 · h + 0.892; 1.18), if at least 4

laminations are glued togetherh) fv,k may be multiplied by kh,v = (600/h)0.13

Characteristic strength values in N/mm2

Bending fm,0,k (51.1) – 59.0a) 81.0

fm,90,k (7.8) – 9.0a) 20.0

Tension ft,0,k (42.3) – 49.0b) – (53.9) (42.3) – 49.0b) – (53.9)

ft,90,edge,k 8.0 8.0 8.0

Compression fc,0,k 62.0c) – (74.4) 62.0c) – (74.4)

fc,90,edge,k 22.0c) – (26.4) 22.0c) – (26.4) 22.0c) – (26.4)

fc,90,flat,k 16.0c) – (19.2) 16.0c) – (19.2)

Shear fv,k 7.8 7.8 3.8

Rolling shear fvR,k 3.8

Stiffness values in N/mm2

Modulus of E0,mean 12,800 12,800

elasticity E0,05 11,800 11,800

E90,edge,mean 2,000 2,000 2,000

E90,edge,05 1,800 1,800 1,800

E90,flat,mean 470 470

E90,flat,05 400 400

Shear Gmean 820 820 430 430

modulus G05 540 540 360 360

Density values in kg/m3

ρk 730

ρmean 800

Table 10: Characteristic values

for Board BauBuche Q

with nominal thickness

27 mm ≤ B ≤ 66 mm in N/mm2

Laminations flatwise edgewise

Characteristic strength values in N/mm2

Bending fm,k (65.0)d) – 70.0 – (91.7) 75.0

Tension ft,0,k (52.0) – 60.0b)e) – (73.0)

ft,90,k 0.6 1.5

Compression fc,0,k service class 1: 59.4g) – (70.0)

service class 2: 49.5f) g) – (58.4)

fc,90,k service class 1: 14.8 service class 1: 14.0

service class 2: 12.3f) service class 2: 11.7f)

Shear fv,k 4.5h) – (5.8) 8.0

Stiffness values in N/mm2

Modulus of E0,mean 16,800

elasticity E0,05 15,300

E90,mean 470

E90,05 400

Shear Gmean 850 760

modulus G05 760 630

Density values in kg/m3

ρk 730

ρmean 800

Table 11: Characteristic

values for Beam

BauBuche GL75 in N/mm2

12

3.2.2 Tensile strength

The characteristic tensile strength value ft,0,k

parallel to the grain may be increased by the coef­

ficient kh,t depending on the larger side length h.

600 0.1kh,t = ――― h = larger side length in mm

h

When adjusting the tensile strength depending on

member length, section 3.1.3 applies analogously.

3.2.3 Shear strength

The characteristic shear strength value fv,k may

be increased by the coefficient kh,v.

600 0.13kh,v = ――― h = member height in mm

h

3.2.4 Compressive strength

Subject to continuous use of the product in ser­

vice class 1, the characteristic value of the com­

pressive strength may be increased by 20 %. In

addition, the value fc,0,k may be multiplied by the

system coefficient kc,0 if at least four laminations

are glued together.

kc,0 = min (0.0009 · h + 0.892 ; 1.18)

where h is the member height in mm.

3.3 Shrinking and swelling

Table 13: Degree of shrinking and swelling for BauBuche

Degree of shrinking/swelling in % for each 1 %

change in moisture content below the fibre

saturation point (around 35 %)

Board S,

GL75

Board Q

Parallel to the grain direction

of the top layer 0.01

Perpendicular to the grain

direction of the top layer 0.40

In the direction of the board

thickness / member height 0.45

Parallel to the grain direction

of the top layer 0.01

Perpendicular to the grain

direction of the top layer 0.03

In the direction of the board

thickness 0.45

3.2 Strength properties for Beam BauBuche GL75

The following considerations are based on the

European Technical Assessment ETA­14/0354 as

of 11.07.2018 and the declaration of performance

PM­008­2018 as of 11.07.2018. For the case

“edgewise loading”, the basic material properties

of the Board BauBuche S in accordance with the

“German general construction technique permit

(Allgemeine Bauartgenehmigung)” no. Z­9.1­838 as

of 19.09.2018 and the declaration of performance

PM­005­2018 as of 27.07.2018 were assumed.

3.2.1 Bending strength

The characteristic strength values may be modi­

fied in the event of bending and shear stress as

well as tensile and compressive stresses parallel

to the grain, if the member height deviates from

600 mm. The reason for this is that the strength

values specified were determined on specimens

that were 600 mm high. For members higher than

600 mm, the following coefficients must be con­

sidered.

For flatwise bending, the characteristic value of

the bending strength fm,k may be multiplied by

the coefficient kh,m.

600 0.1kh,m = ――― h = member height in mm

h

Table 12: Coefficients

Bending

kh,m

1.22

1.17

1.14

1.12

1.10

1.08

1.06

1.05

1.04

1.03

1.02

1.01

1.01

1.00

…

0.92

Tension

kh,t

1.22

1.17

1.14

1.12

1.10

1.08

1.06

1.05

1.04

1.03

1.02

1.01

1.01

1.00

…

0.92

Shear

kh,v

1.30

1.23

1.19

1.15

1.13

1.10

1.09

1.07

1.05

1.04

1.03

1.02

1.01

1.00

…

0.90

Com­

pression

kc,0

1.00

1.00

1.04

1.07

1.11

1.14

1.18

1.18

1.18

1.18

1.18

1.18

1.18

1.18

…

1.18

h in mm

80

120

160

200

240

280

320

360

400

440

480

520

560

600

…

1360

13

The values in Table 13 describe the deformation

behaviour respectively in the board plane or in the

direction of the board thickness / member height.

The values are recommendations of the manu­

facturer.

Generally, stresses triggered by climatic fluctua­

tions must be taken into account. BauBuche is

delivered with a moisture content of 6 % (± 2 %)

and has high degrees of shrinkage and swelling.

To take changes in moisture content and possible

resulting damages into account, particularly dur­

ing erection, an adequate protection of members

and joint areas is required. Further information

can be found in the brochures 03 “Building phys­

ics” and 09 “Wood preservation and surface

treatment”.

3.4 Specific weights to calculate the dead load

DIN EN 1991­1­1 does not specify any value for

the specific weights of laminated veneer lumber

made from beech. We thus advise using the value

from DIN 1055­1. Accordingly, the dead weight of

BauBuche members should be calcula ted based

on a specific weight of 8.5 kN/m3.

3.5 Corrosiveness

In addition to the climatic conditions, the wood

species used influences the risk of corrosion of

metallic fasteners. The key variables are the tannin

content and the pH value of the wood. Beech

wood can be considered “slightly corrosive”.

Beech wood is more likely to cause corrosion

than spruce, but far less likely than oak.

If using metallic fasteners, it is best to ensure a

zinc layer of minimum thickness corresponding to

Table 4.1 of Eurocode 5 or equivalent corrosion

protection. If the approval for the selected fasten­

er allows using a thinner zinc layer or alternative

corrosion protection for installing in beech wood,

deviations from the above reco mmendations

are possible.

4.1 Verifications

4.1.1 General

The timber strength properties differ significantly

when load is applied parallel or perpendicular

to the grain. When designing with BauBuche, it is

therefore important to accurately determine the

direction of the loading and the orientation of

the cross­section. For this reason, e. g. the values

for fc,90,k differ depending on whether loading of

the wide or narrow surface is involved.

The strength values must be taken from the cur­

rent approval / ETA or declaration of performance.

The strength values in this case depend on the

orientation of the member relative to the loading

and the member geometry.

4.1.2 Tension parallel to the grain

The tensile stresses must be verified using the net

cross­section. This means that weaknesses, which

may be caused e. g. by fasteners, must be taken

into consideration. Additional moments are gener­

ated if tensile forces are introduced with an eccen­

tricity, which must be taken into consideration.

σt,0,d ≤ ft,0,d (6.1)

Example 1: Beam BauBuche GL75 tension

member

Load: FEd = 350 kN, kmod = 0.8

Dimensions: 80/120 mm, ℓ = 5 m

The tensile stress is

350 · 103 Nσt,0,d = ―――――――――――― = 36.5 N/mm2

120 mm · 80 mm

The design tensile strength may be increased by

the coefficient kh,t, since the member height is

below 600 mm. In addition, coefficient kℓ has to

be taken into consideration, since the member

length exceeds 3.0 m.

600 0.10 600 0.10kh,t = ――― = ――― = 1.17

h 120

3,000 s/2 3,000 0.12/2kℓ = min ――――― = ――――― = 0.97 = 0.97

ℓ 5,000

1.1

4 ULTIMATE LIMIT STATE

DIN EN 1995­1­1, Chap. 6

DIN EN 1995­1­1 /NA, NCI NA 6

The loads for the verification at the ultimate limit state must be

determined for the persistent and transient design situation.

The strength values must be reduced by the partial factor γM

and the modification factor kmod.

14

4.1.4 Compression perpendicular to the grain

Compressive forces acting on the wide or narrow

surfaces of BauBuche may be verified using an

effective contact area. The contact area on both

sides can be increased by a maximum of 30 mm

parallel to the grain, to take into consideration

the portion of adjacent fibres on the load­bearing

capacity (see Figure 2). An increase in the load­

carrying capacity perpendicular to the grain by the

factor kc,90 in accordance with DIN EN 1995­1­1,

Chap. 6.1.5 is not possible for members made of

BauBuche.

For Board BauBuche, it is important to dis­

tinguish between loading on wide and narrow

surfaces. For loading of narrow surfaces, the

strength is somewhat higher.

The verification of compressive stresses per­

pendicular to the grain reads as

σc,90,d ≤ fc,90,d (6.3)

Figure 2: Effective contact area; dimensions in mm

4.1.5 Compression at an angle to the grain

For compressive stresses at an angle to the grain,

stresses in both parallel and perpendicular to

the grain directions appear. According to (6.16),

the compressive strength for an angle between

the force and grain direction reads

fc,0,kfc, ,k = ――――――――――――――――――― (6.16)

(fc,0,k/fc,90,k) · sin2 + cos2

The verification of compressive stresses at an

angle to the grain reads as

σc, ,d ≤ fc, ,d

Figure 3 shows the decline in compressive

strength with increasing angle . For service

class 1, the values from Figure 3 are slightly

conser vative, since the compressive strength

fc,0,k may be increased by the factor 1.2.

Due to the higher strength fc,90,k for loading on

narrow surfaces, the strength fc, ,k declines

more slowly here. The coefficient kc,0 was not

considered in Figure 3.

ℓ

bef = ℓ + 30 bef = ℓ + 2 · 30 bef = ℓ + 30 + 10

ℓ ℓ30 30 30 30 10

0.8ft,0,d = 1.17 · 0.97 · ――― · 60 N/mm2 = 41.9 N/mm2

1.3

σt,0,d 36.5

η = ―――― = ―――― = 0.87 ≤ 1.0

ft,0,d 41.9

Tension at an angle

For the Board BauBuche Q with cross layers,

separate verification must be performed for stress

at an angle to the grain direction of the top layer.

σt, ,d ≤ k · ft,0,d (NA.58)

where

1k = ―――――――――――――――――――――――― (NA.59) ft,0,d

ft,0,d ――― sin2 + ――― sin · cos + cos2

ft,90,d

fv,d

4.1.3 Compression parallel to the grain

σc,0,d ≤ fc,0,d (6.2)

Instability of members must be taken into

account in accordance with Chapter 4.2.1.

Example 2: Beam BauBuche GL75 compres-

sion member

Load: FEd = 850 kN, kmod = 0.8,

service class 1

Dimensions: 160 /160 mm

The compressive stress is

850 · 103 Nσc,0,d = ―――――――――――― = 33.2 N/mm2

160 mm · 160 mm

The design value of the compressive strength

may be increased in service class 1 by the factor

1.2. In addition, an increase by the coefficient

kc,0 is also possible.

kc,0 = min (0.0009 · h + 0.892 ; 1.18)

= min (0.0009 · 160 + 0.892 ; 1.18)

= min (1.04 ; 1.18) = 1.04

0.8fc,0,d = 1.2 · 1.04 · ――― · 49.5 N/mm2 = 38.0 N/mm2

1.3

33.2η = ―――― = 0.87 ≤ 1.0

38.0

15

Figure 3:

Compressive strength fc, ,k at an angle to the grain

4.1.6 Bending

In the event of biaxial bending, the verification can

be made with linear interaction of the bending

stresses in accordance with equations (6.11) and

(6.12). The factor km = 0.7 allows the small but

highly stressed cross­sectional area for rec­

tangular cross­sections to be positively taken into

consideration. For other cross­sectional shapes,

km shall be set at 1.0.

σm,y,d σm,z,d―――― + km · ―――― ≤ 1 (6.11)

fm,y,d fm,z,d

σm,y,d σm,z,dkm · ―――― + ―――― ≤ 1 (6.12)

fm,y,d fm,z,d

Example 3: Comparison of bending member

made of Beam BauBuche GL75

with Board BauBuche S edgewise

Moment: MEd = 85 kNm, kmod = 0.8

Cross­section: 80/400 mm

The bending stress is

85 · 106 N mm · 6σm,d = ――――――――――――― = 39.8 N/mm2

80 mm · (400 mm)2

The design value of the bending strength of

Beam BauBuche GL75 may be increased by the

coefficient kh,m, since the member height is

under 600 mm.

600 0.10 600 0.10kh,m = ――― = ――― = 1.04

h 400

0.8fm,d = 1.04 · ――― · 75 N/mm2 = 48.1 N/mm2

1.3

39.8η = ―――― = 0.83 ≤ 1.0

48.1

The design value of the bending strength of

Board BauBuche S edgewise must be reduced by

the coefficient kh, since the member height is

between 300 and 1,000 mm.

300 0.12 300 0.12kh = ――― = ――― = 0.97

h 400

0.8fm,d = kh · ――― · 75 N/mm2 = 44.8 N/mm2

1.3

39.8η = ―――― = 0.89 ≤ 1.0

44.8

4.1.7 Shear

The shear strength of cross­sections made of

solid wood and glulam is significantly influenced

by cracks. BauBuche can be considered crack­

free, which eliminates the need to reduce shear

strength and the factor kcr can be used as 1.0.

Shear stresses generated by individual loads near

supports can be discounted, due to the positive

impact of simultaneously acting compressive

stresses in a transverse direction. Loads in this

category include those within a distance h

(support height over centre of support) from the

support edge.

τd ≤ fv,d (6.13)

Example 4: Shear design for

Beam BauBuche GL70

Load: VEd = 60 kN, kmod = 0.8

Cross­section: 140/240 mm

The shear stress is

Vdτd = 1.5 · ――――――

h · b · kcr

60 · 103 N = 1.5 · ――――――――――――――― = 2.68 N/mm2

140 mm · 240 mm · 1.0

The design value of the shear strength may be in­

creased by the coefficient kh,v , since the member

height is under 600 mm.

Wide surface BauBuche S

Narrow surface BauBuche S

GL24h

Wide surface BauBuche Q

Narrow surface BauBuche Q

BauBuche GL7540

fc, ,k in N/mm2

30

50

60

20

10

0

0 ° 10 ° 40 ° 70 °20 ° 50 ° 80 °30 ° 60 ° 90 °

angle

16

kc,y · fc,0,d fm,y,d fm,z,d

σc,0,d σm,y,d σm,z,d――――――― + km · ―――― + ―――― ≤ 1 (6.24)

kc,z · fc,0,d fm,y,d fm,z,d

where

1kc,y = ――――――――――― (6.25)

ky + k2y ­ λ

2rel,y

1kc,z = ――――――――――― (6.26)

kz + k2z ­ λ

2rel,z

where

ky = 0.5 · (1 + βc · (λrel,y ­ 0.3) + λ2rel,y) (6.27)

kz = 0.5 · (1 + βc · (λrel,z ­ 0.3) + λ2rel,z) (6.28)

where βc = 0.1 for glulam and laminated veneer

lumber in accordance with (6.29).

4.2 Stability of members

4.2.1 Buckling of columns

Geometric and material imperfections are inevi­

table within static systems, which is why pure

(central) compression loads are never exerted. Im­

perfections lead to eccentricity of the compres­

sive forces exerted relative to the system line and

thus generate additional bending stresses. For

verifications involving determination of forces and

moments in accordance with first order theory,

this is taken into consideration by using buckling

curves that reduce the compressive strength.

When determining forces and moments in accor­

dance with second order theory or for cross­

sections not exposed to buckling risk (compact

cross­sections that are continuously supported),

the value for kc,y and kc,z in (6.23) and (6.24) can

be taken as 1.0. The term compact applies to

cross­sections with a relative slenderness ratio

λrel,y and λrel,z less than or equal to 0.3.

λy fc,0,k λz fc,0,kλrel,y = ― · ――― ; λrel,z = ― · ――― (6.21); (6.22)

π

E0,05 π E0,05

where

λy/z = ℓef / iy/z

h biy = ――― ; iz = ―――

12

12

ℓef = β · ℓ

Verification of buckling

σc,0,d σm,y,d σm,z,d――――――― + ―――― + km · ―――― ≤ 1 (6.23)

When the loading involves a combination of shear

and torsion, the following condition must be met:

τtor,d τy,d 2 τz,d 2 ―――――――― + ――― + ――― ≤ 1 (NA.56)

kshape · fv,d fv,d fv,d

1.2

kshape

1.1

1.3

1.0

1 2 5 83 64 7 9

ratio h/bFigure 4:

Coefficient kshape for rectangular cross­sections

for rectangular

cross­sections

600 0.13 600 0.13kh,v = ――― = ――― = 1.13

h 240

0.8fv,d = 1.13 · ――― · 4.5 N/mm2 = 3.12 N/mm2

1.3

2.68η = ―――― = 0.86 ≤ 1.0

3.12

With biaxial bending, shear stresses must be

verified by quadratic interaction

τy,d 2 τz,d 2 ――― + ――― ≤ 1 (NA.55)

fv,d fv,d

4.1.8 Torsion

Torsional stresses must be verified in accor­

dance with equation (6.14). When detailing the

support, torsional stress must also be taken into

consideration.

τtor,d ≤ kshape · fv,d (6.14)

For rectangular cross­sections, the torsional

stresses amount to

b Mtor,dτtor,d = 3 · 1 + 0.6 · ― · ――――

h h · b2

The coefficient kshape can be calculated in accor­

dance with (6.15) for rectangular cross­sections

or read from Figure 4.

1 + 0.05 · h

kshape = min

― (6.15)

1.3 b

17

kc,y/z

λy/z Service class 1 Service class 2

GL75 Board S Board Q* GL75 Board S Board Q*

15 1.000 0.997 0.991 1.000 1.000 0.995

20 0.989 0.984 0.973 0.993 0.989 0.980

25 0.975 0.967 0.949 0.981 0.975 0.961

30 0.957 0.945 0.912 0.967 0.958 0.934

35 0.933 0.912 0.851 0.949 0.934 0.892

40 0.898 0.862 0.759 0.924 0.899 0.826

45 0.846 0.788 0.652 0.889 0.848 0.736

50 0.775 0.698 0.552 0.838 0.777 0.638

55 0.691 0.607 0.468 0.772 0.694 0.548

60 0.608 0.526 0.400 0.695 0.611 0.471

65 0.534 0.457 0.344 0.619 0.536 0.408

70 0.469 0.400 0.299 0.549 0.471 0.356

75 0.414 0.352 0.262 0.488 0.416 0.312

80 0.368 0.311 0.232 0.435 0.370 0.276

85 0.328 0.278 0.206 0.389 0.330 0.246

90 0.294 0.249 0.185 0.350 0.296 0.220

95 0.266 0.224 0.166 0.316 0.267 0.198

100 0.241 0.203 0.150 0.287 0.242 0.180

105 0.219 0.185 0.137 0.261 0.220 0.163

110 0.200 0.169 0.125 0.239 0.201 0.149

115 0.184 0.155 0.114 0.219 0.185 0.137

120 0.169 0.142 0.105 0.202 0.170 0.126

kc,y/z

λy/z Service class 1 Service class 2

GL75 Board S Board Q* GL75 Board S Board Q*

125 0.156 0.131 0.097 0.186 0.157 0.116

130 0.145 0.122 0.090 0.173 0.145 0.108

135 0.134 0.113 0.083 0.161 0.135 0.100

140 0.125 0.105 0.078 0.150 0.126 0.093

145 0.117 0.098 0.072 0.140 0.117 0.087

150 0.109 0.092 0.068 0.131 0.110 0.081

155 0.102 0.086 0.064 0.123 0.103 0.076

160 0.096 0.081 0.060 0.115 0.097 0.071

165 0.091 0.076 0.056 0.108 0.091 0.067

170 0.085 0.072 0.053 0.102 0.086 0.063

175 0.081 0.068 0.050 0.097 0.081 0.060

180 0.076 0.064 0.047 0.091 0.077 0.057

185 0.072 0.061 0.045 0.087 0.073 0.054

190 0.069 0.058 0.042 0.082 0.069 0.051

195 0.065 0.055 0.040 0.078 0.066 0.048

200 0.062 0.052 0.038 0.074 0.062 0.046

205 0.059 0.050 0.037 0.071 0.059 0.044

210 0.056 0.047 0.035 0.067 0.057 0.042

215 0.054 0.045 0.033 0.064 0.054 0.040

220 0.051 0.043 0.032 0.062 0.052 0.038

225 0.049 0.041 0.030 0.059 0.049 0.036

230 0.047 0.040 0.029 0.056 0.047 0.035

Example 5: Columns made of BauBuche GL75

Load: FEd = 50 kN, kmod = 0.9, Service class 2

Dimensions: 100/120 mm, ℓ = 4 m

The compressive stress is

50 · 103 Nσc,0,d = ―――――――――――― = 4.17 N/mm2

100 mm · 120 mm

where 4.00 mλz = ―――――――――― = 139

0.10 m / 12

which can be read from Table 14 for kc,z at

round 0.152.

The stability verification is covered by

σc,0,d 4.17 N/mm2

η = ―――――――― = ――――――――――――― = 0.80 ≤ 1

kc,z · fc,0,d · kc,0 0.152 · 34.3 N/mm2 · 1,0

Table 14: Coefficient kc,y/z depending on λy/z for Board BauBuche and Beam BauBuche GL75

* Values apply for Board BauBuche Q with a nominal thickness of 27 mm < B < 66 mm as well as for Board BauBuche Q with a nominal

thickness B < 24 mm

Figure 5: Buckling

length coefficient β

(Euler)

Case 1 Case 2 Case 3

Case 4

ℓ

β = 2ℓ

β = ℓ β = 0.699ℓ

β = ℓ/2

NKi NKi NKi

NKi

18

4.2.2 Lateral torsional buckling

Similar to the case of buckling of compression

members, slender beams under vertical loading

are prone to a lateral buckling of the compressed

edge and thus torsion of the cross­section.

Using buckling curves, the bending stresses are

compared with a reduced bending strength

depending on the material and geometry of the

beam.

The relative slenderness ratio for bending is

ℓef · Wy fm,kλrel,m = ―――――― · ―――――――――― (6.30); (6.31)

Iz · Itor π E0,05 · G0,05

For beams made of BauBuche GL75 the product

of the 5 %­quantile of the stiffness variables

E0,05 · G0,05 may be multiplied by the factor 1.2.

When calculating the relative slenderness ratio,

subdividing into a geometric and material coeffi­

cient is possible.

The material coefficient

κm = fm,k / (π · E0,05 · G0,05) thus amounts to e. g.

75 / (π · 15,300 · 760 · 1.2) =0.08.

The geometric coefficient may, depending on the

ratio h to b, be read from Figure 6. Accordingly,

the expression can be simplified to

λrel,m = ℓef · κm · κg (ℓef in mm)

The effective lengths of beams with load intro­

duction in the centre of gravity are calculated in

this case in accordance with Table 15 from the

beam length or the distance of the bracing ele­

ments. For loads applied at the compressed edge,

ℓef has to be increased by 2 h, and for loads ap­

plied at the tensile edge, ℓef may be reduced by

0.5 h. The prerequisite in each case is ensuring

sufficient torsional support (torsional restraints).

The coefficient for reduction of the bending

strength to take into consideration additional

stresses due to lateral buckling is thus

1.0 λrel,m ≤ 0.75

kcrit = 1.56 ­ 0.75 · λrel,m ; 0.75 < λrel,m ≤ 1.4 (6.34)

1 / λ2rel,m 1.4 < λrel,m

For bending stress only, the following verification

must be met

σm,d ≤ kcrit · fm,d (6.33)

With combined bending and compressive stress,

the result is

σm,d 2 σc,0,d ――――――― + ――――――― ≤ 1 (6.35)

kcrit · fm,d kc,z · fc,0,d

Example 6: Lateral torsional buckling design

of Beam BauBuche GL75

Moment: MEd = 156 kNm, kmod = 0.9,

service class 1

Dimensions: 140/560 mm, ℓ = 10 m

The bending stress is

156 · 106 Nmm · 6σm,d = ―――――――――――――― = 21.3 N/mm2

140 mm · (560 mm)2

The geometric coefficient κg can be read in

accordance with Figure 6 at around 0.175.

Accordingly, the related degree of slenderness

λrel,m = 0.9 · 10 · 103 · 0.175 · 0.08 = 1.33

and

Geometric

coefficient κg

0.08

0.12

0.16

0.20

0.24

0.28

0.32

0.36

0.40

0.44

50 100 150 200 250 300

Figure 6: Geometric coefficient κg for varying ratios h/b

depending on member width b

h/b

10

8

6

43

2

Member width b in mm

Table 15: Effective length for members prone to

lateral torsional buckling

Type Load ℓef/ℓ

Single­span Constant bending moment 1.0

beams Uniformly distributed load 0.9

Single load in the centre

of the span 0.8

Cantilever Uniformly distributed load 0.5

beams Single load at the free

cantilever end 0.8

19

kcrit = 1.56 ­ 0.75 · λrel,m = 0.56 for 0.75 < λrel,m ≤ 1.4

The stability verification is covered by

σm,d

η = ――――――――――――――― fm,k kcrit · kmod · kh,m · ―――

γM

21.3

= ――――――――――――――― = 0.78 ≤ 1.0 75 0.56 · 0.9 · 1.01 · ―――

1.3

For biaxial bending and cross­sectional ratios of

h/b ≤ 4, verification is performed as follows

σc,0,d σm,y,d σm,z,d 2――――――― + ――――――― + ―――― ≤ 1 (NA.60)

kc,y · fc,0,d kcrit · fm,y,d fm,z,d

σc,0,d σm,y,d 2 σm,z,d――――――― + ――――――― + ―――― ≤ 1 (NA.61)

kc,z · fc,0,d kcrit · fm,y,d fm,z,d

4.3 Beams with variable cross­sections

4.3.1 Single tapered beams

For single tapered beams made of Board Bau­

Buche (edgewise) with tapered edge, the bending

stresses are verified at point xσ,max where the

stress peaks.

Additional shear stresses and stresses perpendic­

ular to the grain are generated along the tapered

edge. This stress interaction is taken into consid­

eration by reducing the bending strength fm,k by

the factor km, . In the process, a distinction is

made between tensile and compressive stresses

at the tapered edge.

σm, ,d ≤ km, · fm,d (6.38)

where km, denotes tensile stresses at the tapered

edge of the Board BauBuche S

1km, = ――――――――――――――――――――――――― (6.39) fm,d fm,d 1 + ――――――― tan

2 + ―――― ― tan2

2

0.75 · fv,d ft,90,d

and of the Board BauBuche Q

1km, = ――――――――――――――――――――――――― fm,d fm,d 1 + ―――――― tan

2 + ―――― tan2

2

fv,d ft,90,d

or compressive stresses at the tapered edge of

the Board BauBuche S

1km, = ――――――――――――――――――――――――― (6.40) fm,d fm,d 1 + ――――――― tan

2 + ―――― ― tan2

2

1.5 · fv,d fc,90,d

and of the Board BauBuche Q

1km, = ――――――――――――――――――――――――― fm,d fm,d 1 + ―――――― tan

2 + ―――― tan2

2

fv,d fc,90,d

The taper angle is to be limited to 24°.

The location of the governing cross­section xσ,max

for a beam with a uniformly distributed load is at

ℓxσ,max = ―――――――――

1 + hap / hs

where hap indicates the maximum member height

and hs the minimum member height.

4.3.2 Double-tapered beams

The member halves of double­tapered beams can

be considered as single tapered beams and verified

with regard to stress interaction in accordance

with Chapter 4.3.1.

The variable beam height results in a non­linear

distribution of bending stress. The bending stress for

the verification in the apex area is thus determined

with the coefficient kℓ in accordance with (6.43).

Figure 7: Coefficient km, for tapered edge subject to

tensile and compressive stresses of beams Board

BauBuche (edgewise) S and Q (B > 27 mm). The bending

strength was reduced acc. to (3.3) for a beam with

height h = 1000 mm.

km,

Compression

Tension

angle in [°]

Tension BauBuche S

Compression BauBuche S

Tension BauBuche Q

Compression BauBuche Q

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5 10 15 20 25

Inclinazione in (º)

20

The maximum tensile stress perpendicular to the

grain due to bending stress is

6 · Map,dσt,90,d = kp · ―――――― (6.54)

b · h2

ap

where

kp = 0.2 · tan ap (6.56)

4.4 Notched members

The main purpose of notches at supports is to

reduce the height of members. High tensile

stresses perpendicular to the grain and shear

stresses are generated, which can lead to cracks

originating from the notch corner. The accelerat­

ed change of humidity via the end grain areas also

exacerbates the cracking risk.

The use of Board BauBuche Q (edgewise) ge nerally

avoids the risk of cracks, since the transverse

layers act as reinforcement and help transfer

tensile forces perpendicular to the grain.

1.5 · Vdτd = ――――― ≤ kv · fv,d (6.60)

b · hef

For beams with a notch on the opposite side of

the support, kv = 1.0 may be assumed. The follow­

ing applies for a beam notched on the support side

1.0

1.1 · i1.5 kn 1 + ―――――

kv = min h

h (1 ­ ) + 0.8 x― 1― ­ 2

(6.62)

h

where

i Incline of the notch

ℓA i = cotε = ―――――

h ­ hef

(i = 0 for right angle notches)

kn = 4.5 for laminated veneer lumber (6.63)

hef

= ―― Height h of the beam, reduced

h

height hef at the notched support

x Distance between notch corner and

support reaction

For beams with notches on the opposite side of

the support, kv = 1. If x < hef, kv may be deter­

mined in accordance with equation (NA.62)

h (h ­ hef) · xkv = ――― · 1 ­ ―――――――― (NA.62)

hef h · hef

Example 7: Comparison of rectangular notch

in Beam BauBuche GL75 and

Board BauBuche Q

Load: governing shear force Vd = 6.0 kN,

kmod = 0.8

Dimensions: beam 50 /200 mm

height at support hef = 120 mm

distance to the notch x = 75 mm

Figure 8: Notch with tensile / shear crack

hef = hh

ε

i1

X ℓA

6 · Map,dσm,d = kℓ · ――――――― ≤ fm,d (6.41); (6.42)

b · h2

ap

where

kℓ = k1 = 1 + 1.4 · tan ap + 5.4 · tan2 ap (6.43); (6.44)

where hap indicates the member apex height and

ap the taper angle of the beam in the apex area.

The kink of the member axis in the apex generates

deviation forces, which lead to tensile stresses

perpendicular to the grain. The following condition

must be met

σt,90,d ≤ kdis · kvol · ft,90,d (6.50)

where

kdis = 1.4 (6.52)

0.01 m3 0.2kvol = ――――――

V

0.01 m3 0.2 = ―――――――――――――――――― (6.51)

h2

ap · b · (1 ­ 0.25 · tan ap)

21

4.5 Step joints

Step joints are “carpentry” connections to join

inclined members, e. g. struts to timber chords.

In this case, the compressive force is introduced

by compression in the contact area and trans­

ferred by shear stress. Classic versions employing

this approach include the single step and heel

joint as well as the double step joint as a combi­

nation of both types. In addition, a version involv­

ing multiple con catenated heel joints (“multiple

step joint”) was developed. The advantages of

this shape include the low cutting depths, a

central compressive force in the strut, the short

end length as well as a high connection stiffness.

Multiple step joints may be designed in accor­

dance with Enders­Comberg and Blass (2014).

Further information can be found in brochure 05

“Fasteners”.

Note: Step joints are not covered in Eurocode 5.

This document therefore specifies the calculation

principles of the NA­Germany. Where required, its

applicability outside Germany should be checked.

Figure 9: Double step joint

Beam BauBuche GL75:

Shear stress at the notch

1.5 · Vd 1.5 · 6.0 · 103 Nτd = ――――― = ―――――――――――― = 1.50 N/mm2

b · hef 50 mm · 120 mm

Reduction coefficient kv

1.0 4.5kv = min ―――――――――――――――――――――――――――

200 0.6 · (1 ­ 0.6) + 0.8 75 1

­ 0.62

200 0.6

= 0.382

where kmodfv,d = kv · ―――― · kh,v · fv,k

γM

0.8= 0.382 · ――― · 1.15 · 4.5 N/mm2 = 1.22 N/mm2

1.3

verification:

1.50η = ――――― = 1.23 > 1.0!!!

1.22

Board BauBuche Q:

The transverse layers are considered reinforcing

elements.

The tensile force to be transferred is calculated

in accordance with Chapter 9.3.2.

Ft,90,d = 1.3 · Vd · [ 3 · (1 ­ )2 ­ 2 · (1 ­ )3]

= 1.3 · 6.0 · [ 3 · (1 ­ 0.6)2 ­ 2 · (1 ­ 0.6)3] = 2.75 kN

(NA.77)

According to (NA.84), the transverse layers for the

verification may only be taken into account within

ℓr ≤ 0.5 · (h ­ hef) = 0.5 · 80 = 40 mm

Accordingly, the verification of perpendicular to

grain tensile stresses reads

σt,d 1.38 N/mm2

2.0 · ――― = 2.0 · ―――――――― = 0.56 ≤ 1.0 (NA.82)

ft,d 4.9 N/mm2

where

Ft,90,d 2.75 · 103 Nσt,d = ―――― = ――――――――――― = 1.38 N/mm2

tr · ℓr 50 mm · 40 mm

(NA.83)

8 N/mm2

ft,90,d = 0.8 · ―――――――― = 4.9 N/mm2

1.3

Note: The entire beam width is applied as the

thickness of the reinforcement panel tr. For this

purpose, the perpendicular to grain tensile

strength is assumed as ft,90,d.

The reinforcing effect of the transverse layers

means the shear stresses can be verified without

the need to consider kv

1.50η = ―――― = 0.31 ≤ 1.0

4.80

with the design value of edgewise shear strength

0.8fv,d = ――― · 7.8 N/mm2 = 4.8 N/mm2

1.3

The transverse layers allow the load­carrying capa­

city of the supports to be significantly increased.

h

β/2

β/2

tv1

ℓv1

ℓv2

tv2γ/2 γ

γ

F

F1 F2

22

Note: For the Beam BauBuche GL75 (laminations

edgewise) the shear strength of fv,k = 8.0 N/mm2

can be used as the value of the basic material

(Board BauBuche S). When using 8.0 N/mm2 as

the characteristic value of the shear strength,

the coefficient kh,v > 1 must not be applied.

Accordingly, the capacity per contact area can

be determined

fc,γ / 2,d · b · tv,1FR1,d = ――――――――― (single step joint)

cos2 (γ/2)

fc,γ,d · b · tv,2FR2,d = ――――――――― (heel joint)

cos γ

FR1,d + FR2,d ≥ Fd

Verification of shear forces in the loaded end

τd Fd · cos γ――― ≤ 1 where τd = ―――――――

fv,d b · ℓv

The required loaded end lengths are thus

FR1,d · Fd · cos γℓv,1 = ――――――――――――――― (single step joint)

(FR1,d + FR2,d ) · b · fv,d

FR2,d · Fd · cos γℓv,2 = ――――――――――――――― (heel joint)

(FR1,d + FR2,d ) · b · fv,d

For required loaded end lengths ℓv exceeding

8 · tv, verification is deemed as non­compliant.

The cutting depths tv should meet the following

conditions

h/4 für γ ≤ 50° (NA.160)

tv ≤ h/6 für γ > 60° or cutting from both sides

For double step joints, the cutting depth tv of the

heel joint should be selected to be larger than that

of the single step joint, to ensure the end result is

two separate shear surfaces in the timber chord.

Example 8: Double step joint for

Beam BauBuche GL75

Load: Strut force Fd = 140 kN

kmod = 0.9, service class 1

Dimensions: Strut (edgewise) 120/120 mm

Chord 120/200 mm

Connection angle γ = 35°

Cutting depths tv,1 = 20 mm

tv,2 = 25 mm

Design values for Beam BauBuche GL75:

0.9fc,0,d = 1.2 · ――― · 49.5 N/mm2 = 41.1 N/mm2

1.3

0.9fc,90,d = ――― · 14.0 N/mm2 = 9.69 N/mm2

1.3

0.9fv,d = ――― · 8.0 N/mm2 = 5.54 N/mm2

1.3

In accordance with (NA.163)

fc,17,5°,d = 29.1 N/mm2

fc,35°,d = 20.6 N/mm2

The capacity of the single step area is

29.1 · 120 · 20 · 10 ­3

FR1,d = ――――――――――――― = 76.8 kN

cos2 (17.5°)

and of the heel joint area

20.6 · 120 · 25 · 10 ­3

FR2,d = ――――――――――――― = 75.5 kN cos 35°

Fd 140η = ―――――――― = ―――――――― = 0.92 ≤ 1.0 FR1,d + FR2,d 76.8 + 75.5

The required loaded end lengths amount to

76.8 · 140 · 103 · cos 35°ℓv,1 = ―――――――――――――――――

(76.8 + 75.5) · 120 · 5.54

= 87.0 mm ≤ 8 · tv,1 = 160 mm

75.5 · 140 · 103 · cos 35°ℓv,2 = ―――――――――――――――――

(76.8 + 75.5) · 120 · 5.54

= 85.5 mm ≤ 8 · tv,2 = 200 mm

In this example, the load­carrying capacity can

be increased by 12 % if “multiple step joints”

are used whilst simultaneously reducing cutting

depth and loaded end length. Precise (CNC)

machining of the multiple step joint is required.

Verification of compressive stresses in the

contact area:

σc, ,d

―――― ≤ 1 (NA.161)

fc, ,d

where

Fc, ,d σc, ,d = ―――― (NA.162)

A

fc,0,dfc, ,d = ――――――――――――――――――――――――――――――――― fc,0,d fc,0,d ――――――― sin2

2 + ――――― sin · cos

2+ cos4

2 · fc,90,d 2 · fv,d

(NA.163)

23

5.1 General points

In serviceability limit states, Eurocode 5 tends to

employ “should” instead of “shall”. To guarantee

the long­term and undisturbed use of a construc­

tion, individual members must comply with re­

quirements governing deformation and vibration

behaviour as well as requirements in terms of the

load­carrying capacity. Accordingly, deformation

and vibration analyses in static calculations are

required. The limit values to be complied with

should be agreed with the building owner.

5.2 Deformations

The initial deformation uinst can be calculated

using applicable design tables depending on

the system and the characteristic loading.

The mean value should always be used for the

modulus of elasticity, the shear and the slip

modulus (E0(90),mean, Gmean, Kmean).

The creep of the wood exacerbates the defor­

mation of the member over the duration of the

load. This is taken into consideration by the

coefficient kdef.

The initial deformation uinst is:

uinst = uinst,G + ∑uinst,Q,i

The final deformation ufin is:

ufin = ufin,G + ufin,Q,1 + ∑ufin,Q,i (2.2)

where

ufin,G = uinst,G · (1 + kdef) (2.3)

ufin,Q,1 = uinst,Q,1 · (1 + ψ2,1 · kdef) (2.4)

ufin,Q,i = uinst,Q,i · (ψ0,i + ψ2,i · kdef) ; i > 1 (2.5)

The initial deformation for a single­span girder

with uniformly distributed load is calculated with

5 qk · ℓ4

uinst = ――― · ―――――――

384 E0,mean · I

and for a cantilever beam with

qk · ℓ4

uinst = ――――――――――

8 · E0,mean · I

The total final deformation unet,fin is:

unet,fin = unet,fin,G + ∑unet,fin,Q,i ­ uc (NA.1)

where

unet,fin,G = uinst,G · (1 + kdef)

unet,fin,Q,i = uinst,Q,i · ψ2,i · (1 + kdef)

uc = Camber

Eurocode 5, NA ­ NDP at 7.2(2), Tab. NA.13

specifies limit values for the deformations to be

complied with.

Table 16: Recommended limit values for deformation of

bending members

Tab. NA. 13, row 2 applies for pre­cambered or

secondary members.

Example 9: Deformation verification for a

single-span girder

Uniformly distributed load, Beam BauBuche GL75,

120 / 240 mm

Loads: Dead weight gk = 1.40 kN/m2

Live load (Cat. A) pk = 2.80 kN/m2

kdef = 0.6; ψ2 = 0.3 ; service class 1

Dimensions: Span ℓ = 6 m

Second moment Iy = 1.38 · 108 mm4

of area

Beam spacing ℮ = 0.625 m

5 SERVICEABILITY LIMIT STATE

DIN EN 1995­1­1, Chap. 2.2

DIN EN 1995­1­1, Chap. 7

uinst ufin unet,fin

Single­span beams ℓ / 300 ℓ / 200 ℓ / 300

Cantilever beams ℓ / 150 ℓ / 100 ℓ / 150

24

5.3 Vibrations

5.3.1 General points

Disruptive vibrations are actually likely to occur in

one of the most popular examples of timber con­

struction, namely lightweight floor constructions.

The following section introduces two methods to

calculate the vibration behaviour of apartment

floors according to Blaß et al. (2005).

Various checks may be required to verify the ser­

viceability of floors depending on the frequency

range.

The Eigenfrequency of the floor can be deter­

mined in simplified form via the bending stiffness

of floor beams (without sheathing). In general,

the bending stiffness of screed may be calculated

assuming no composite action.

π E · If1 = kf · ―――― · ――――

2 · ℓ2

m · e

where

m Mass under quasi­permanent load

(g + ψ2 · p) in kg/m²

ℓ Floor span in m

E · I Bending stiffness of floor beams in Nm2

℮ Beam spacing in m

kf Coefficient in accordance with Table 19

By considering floor beams as mechanically joint­

ed beams with an effective flange width of the

sheathing (see Chapter 9.4.2 γ­Method), improved

vibration calculations can be obtained.

If no exact values for the modal damping ratio

exist, the value ξ of 0.01 is recommended.

Verification of elastic initial deformation:

uinst = uinst,G + uinst,Q = 6.37 + 12.7 ≤ l/300

= 19.1 mm ≤ 20 mm

where 5 gk · ℓ

4

uinst,G = ――― · ―――――――

384 E0,mean · I

5 0.875 · 6,0004

= ――― · ――――――――――――― = 6.37 mm

384 16,800 · 1.38 · 108

5 pk · ℓ4

uinst,Q = ――― · ―――――――

384 E0,mean · I

5 1.75 · 6,0004

= ――― · ――――――――――――― = 12.7 mm

384 16,800 · 1.38 · 108

Verification of final deformation:

ufin = ufin,G + ufin,Q,1 ≤ ℓ/200

= 10.2 + 15.0 = 25.2 mm ≤ 30 mm

where

ufin,G = uinst,G · (1 + kdef) = 6.37 · (1 + 0.6) = 10.2 mm

ufin,Q = uinst,Q · (1 + ψ2,1 · kdef)

= 12.7 · (1 + 0.3 · 0.6) = 15.0 mm

Verification of total final deformation:

unet,fin = unet,fin,G + unet,fin,Q ≤ ℓ/300

= 10.2 + 6.10 = 16.3 mm ≤ 20 mm

where

unet,fin,G = uinst,G · (1 + kdef) = 6.37 · (1 + 0.6) = 10.2 mm

unet,fin,Q = uinst,Q · ψ2,1 · (1 + kdef)

= 12.7 · 0.3 · (1 + 0.6) = 6.10 mm

Table 17 shows that deformations of a glulam

cross­section made of softwood, while having

the same dimensions and loads, exceed the

above­calculated values by around 50 %.

Table 17: Comparison of the deformations of the

Beam BauBuche GL75 and softwood glulam beam

GL24h in mm

uinst ufin unet,fin

BauBuche GL75 19.1 25.2 16.3

GL24h 27.7 36.5 23.6

Table 18: Damping ratio in accordance with SIA 265 and

ÖNORM B 1995­1­1:2015 + NA

Floor construction ξ

Floors without floating screed resp.

lightweight floor construction 0.01

Floors with floating screed 0.02

Timber floors and mechanically

laminated timber floors

with floating screed 0.03

25

5.3.2 Method in accordance with Blass et al.

(2005)

For floors with natural frequencies exceeding

8 Hz, the following load situations must be

examined more closely:

(1) Deflection due to single load F

(2) Speed due to unit impulse

Floors with natural frequencies of under 8 Hz

require specific examinations. Examinations (3)

and (4) according to Blass et al. (2005) are

re commended.

(3) Examination of the vibration velocity for the

load case “heel impact”

(4) Acceleration; examination of resonance

The following section presents examinations of

the vibration behaviour using two examples.

Example 10: Vibration verification for a timber

floor (f1 < 8 Hz)

Single­span girder made of Beam BauBuche GL75

120/240 mm

Loads:

Dead weight gk = 1.40 kN/m2

Live load (Cat. A) pk = 2.80 kN/m2

ψ2 = 0.3

quasi­permanent

combination qk = 1.40 + 0.3 · 2.80

= 2.24 kN/m2

Input parameters:

Mass m = 2.24/9.81 · 1,000

= 228 kg/m2

Beam span ℓ = 6 m

Floor panel width b = 8 m

Beam spacing ℮ = 0.625 m

Second moment of area Iy = 1.38 · 108 mm4

Damping ratio ξ = 0.01 (Table 18)

Eigen frequency

π EIBeamf1 = kf · ―――― · ――――――

2 · ℓ2

m · e

π 1.68 · 1010 N/m2 · 1.38 · 10­4 m4

= 1.0 · ――――― · ―――――――――――――――――――

2 · (6 m)2

228 · 0.625 m

= 5.56 Hz < 8 Hz

where

kf = 1.0 for single­span girder

Since the natural frequency is below 8 Hz,

examinations (3) and (4) are required.

(3) Load case “heel impact”

Initial deflection due to a vertical static single load

F (1 kN):

F · ℓ3 1 · 103 N · (6,000 mm)3

u = ―――― = ――――――――――――――――――――――――

48 · EI

48 · 1.68 · 104 N/mm2 · 1.38 · 108 mm4

= 1.94 mm

With Table 21 b results as 80 when applying a to:

u 1.94 mma ≥ ― = ―――――― = 1.94 mm/kN

F

1 kN

Accordingly, the vibration velocity v can be deter­

mined:

55v ≈ ――――――――――――――

m · e · ℓ / 2 · γ + 50

55 ≈ ――――――――――――――――――――――― = 0.115 m/s

228 kg/m2 · 0.625 m · 6 m / 2 · 1.0 + 50

where

γ = 1.0 since single­span girder

The following limit value should be complied with:

vlimit = 6 · b(f1 · ξ ­ 1) = 6 · 80 (5.4 · 0.01 ­ 1) = 0.096 m/s

The vibration velocity is thus slightly above the

limit value. If we consider the floor as a set of

mechanically connected beams, verification might

be met.

(4) Acceleration; examination of resonance

Calculation of the dominant vertical acceleration

56 1 56 1a ≈ ―――――― · ― = ――――――――――――――― · ―――

m · b · ℓ · γ ξ

228 kg/m2 · 8 m · 6 m · 1.0 0.01

= 0.51 m/s2

According to Blass et al. (2005) the following limit

values apply:

a < 0.1 m/s2 Well­being

a < 0.35 – 0.7 m/s2 Noticeable, but not

unpleasant

a > 0.7 m/s2 Disruptive

26

Example 11: Vibration verification for a

timber floor (> 8 Hz)

Two­span beam made of Beam BauBuche GL75

160/280 mm

Loads:

Dead load gk = 1.50 kN/m2

Live load (Cat. A) pk = 2.80 kN/m2

ψ2 = 0.3

Quasi­continuous qk = 1.50 + 0.3 · 2.80

combination = 2.34 kN/m2

Characteristic values:

Mass m = 2.34/9.81 · 1,000

= 239 kg/m2

Long span ℓ = 6.25 m

Short span ℓ1 = 4 m

Floor panel width B = 9 m

Beam spacing ℮ = 0.625 m

Second moment of area Iy = 2.93 · 108 mm4

Damping ratio ξ = 0.01 (Table 18)

Natural frequency taking into account the effect

of continuous beam

π EIBeam f1 = kf · ―――― · ――――――

2 · ℓ2

m · e

π

1.68 · 1010 N/m2 · 2.93 · 10­4 m4

= 1.224 · ―――――――― · ――――――――――――――――――― 2 · (6.25 m)2 239 · 0.625 m

= 8.93 Hz > 8 Hz

where

kf = 1.224 from Table 19 (interpolated) for ℓ1 / ℓ = 4 /

6.25 = 0.64

For frequencies above 8 Hz, the aforementioned

requirements (1) and (2) must be met:

(1) Deflection due to single load F = 1 kN

F · ℓ3

u = ――――

48 · EI

1 · 103 N · (6,250 mm)3 = ――――――――――――――――――――――――

48 · 1.68 · 104 N/mm2 · 2.93 · 108 mm4

= 1,03 mm

The deflection is within the range between 0.5 and

4.0 mm. This means requirement (1) has been met.

(2) Unit impulse velocity

1v ≈――――――――――――――

m · e · ℓ / 2 · γ + 50

1 ≈――――――――――――――――――――――――― = 0.0019m/s

239 kg/m2 · 0.625 m · 6.25 m / 2 · 1.02 + 50

where

γ = 1.02 from Table 20 (interpolated)

u 1.04 mma ≥ ―― = ―――――― = 1.04 mm/ kN

F 1 kN

using Table 21 a value for b = 120 is calculated

vlimit = b(f1 · ξ ­ 1) = 120 (8.93 · 0,01 ­ 1) = 0.013 m/s > v

Table 19: Coefficient kf to take into account the effect of continuous beams according to Blass et al. (2005); where

ℓ1 is the smaller span length and ℓ the longer span length

Table 20: Coefficient depending on the span ratio to the adjacent span, according to Blass et al. (2005); where ℓ1 is

the smaller span length and ℓ the longer span length

Lower values of a indicate better vibration behaviour. If stringent demands are imposed on the member

behaviour (e. g. public buildings), a should not exceed the value of 1.0.

For single­span girders, coefficients kf and γ are to be set at 1.0.

Table 21: Coefficient b according to Figure 7.2 DIN EN 1995­1­1

ℓ1 / ℓ 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

kf 1.00 1.09 1.15 1.20 1.24 1.27 1.30 1.3 3 1.3 8 1.42 1.56

ℓ1 / ℓ 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

γ 2.00 1.40 1.15 1.05 1.00 0.969 0.951 0.934 0.927 0.918 0.912

a 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0

b 150 144 138 132 126 120 112 104 96 88 80 77 74 71 68 65 62 59 56 53 50

27

5.3.3 Method in accordance with ÖNORM B

1995-1-1:2015 + NA

The following regulations are applicable to floors,

which can be classified in accordance with Table

The Eigenfrequency f1 should be considered for

the verification of the frequency criterion, see also

section 5.3.1. Further information concerning

floors with transverse load distribution can be

taken from ÖNORM B 1995­1­1:2015.

If the considered floor is not simply supported,

the Eigenfrequency f1 may be multiplied by the

coefficient ke,1 in accordance with Table 24.

22. Separate investigations are required for light­

weight floors with masses below 50 kg/m2 or with

a particular usage.

Tabella 23: Limit values for the frequency and stiffness criteria and vibration acceleration in accordance with ÖNORM B 1995­1­1:2015,

Tab NA.7.2.­E4 and Tab NA.7.2.­E6

b Grit fill with a mass of at least 60 kg/m3 is called

heavy grit fill.

Table 22: Typical usage and structural requirements of floor classes in

accordance with ÖNORM B 1995­1­1:2015, Tab NA.7.2.­E1

Floor made

of timber

beams

Floor made

of massive

timber

panels

With (heavy) screed

Dry floor (e.g. with

gypsum fibre boards)

With (heavy) screed

Dry floor (e.g. with

gypsum fibre boards)

Typical usage

Limit value for frequency criterion

Limit value for stiffness criterion

For floor constructions with

Limit value for vibration acceleration

Structural requirements

Floor class 1

– Floors between different

units of use (also continu­

ous floors)

– Apartment partitioning floors

in multiple family units,

– Office floors with PCs or

meeting rooms

– Short­span corridors

Floor class 1

f1 ≥ flimit = 8 Hz

wstat ≤ wlimit = 0.25 mm

4.5 Hz ≤ f1 ≤ 8 Hz

arms ≤ alimit = 0.05 m/s2

Floating with heavy grit fillb

Separate verification

required

Floating with heavy or light­

weight grit fillb

Floating with heavy grit fillb

Floor class 2

– Floors within a unit

of use,

– Floors in normal

single­family homes

Floor class 2

f1 ≥ flimit = 6 Hz

wstat ≤ wlimit = 0.5 mm

4.5 Hz ≤ f1 ≤ 6 Hz

arms ≤ alimit = 0.10 m/s2

Floating

(also without grit fill)

Floating with heavy

grit fillb

Floating

(also without grit fill)

Floating with heavy

grit fillb

–

–

–

–

Floor class 3

– Floors under unused

rooms or undevel­

oped attic spaces,

– No requirements

in terms of vibration

behaviour

Floor class 3

–

–

–

–

The Eigenfrequency f1 of a two­span floor may be

multiplied by the coefficient kf in accordance with

Table 19.

Support conditions

(without transverse load distribution) ke,1

pinned – pinned 1.000

fixed – pinned 1.562

fixed – fixed 2.268

fixed – free (cantilever) 0.356

Table 24: Coefficients ke,1 to consider different support

conditions

28

6 CONNECTIONS WITH DOWEL-TYPE

METALLIC FASTENERS

DIN EN 1995­1­1, Chap. 8

6.1 Load­carrying capacity of connections with

laterally loaded fasteners

Depending on the geometry and bending resis­

tance of fasteners as well as the embedding

strength (resistance against the pushing­in of the

fastener) of the wood, the load­carrying capacity

of connections with laterally loaded, dowel­type

fasteners can be determined, assuming ductile

failure and based on the Johansen theory. Plastic

failure of both the wood under the impact of

embedding stress as well as the fasteners under

bending moments is presumed. Focusing on the

following points during the design can help avoid

sudden brittle failures:

– Use of slender fasteners

– Use of lower strength steel grades

– Avoiding low fastener spacing or end and

edge distances

Chapters 8.2.2 and 8.2.3 of Eurocode 5 specify

equations used to determine the characteristic

load­carrying capacities of timber­to­timber

connections and steel­to­timber connections.

The failure modes taken into consideration in

this case are shown in Figure 10 and Figure 11.

Verification

A minimum value of f1,min ≥ 4.5 Hz of the Eigen­

frequency is required for floor classes 1 and 2 in

accordance with Table 23.

Vibrations of floor classes 1 to 3 in accordance

with Table 22 are considered verified if the limit

values for the frequency and stiffness criteria in

accordance with Table 23 are met. The limit value

for vibration acceleration must additionally be

met for floor constructions with f1,min ≤ f1 ≤ fgr.

The largest vertical initial deformation wstat caused

by a single load F = 1 kN acting at the most un­

favourable position and taking the effective width

bf into account must be calculated to verify the

stiffness criterion. For continuous floor systems,

the largest floor span may be considered.

F · ℓ3

wstat = ――――――――― NA.7.2­E2

48 · (E · I)ℓ · bF

where

Wstat Vertical initial deformation caused by

F = 1 kN, in m

F Single load F = 1 kN, in N

(E · I)ℓ Bending stiffness of floor, in Nm2/m

ℓ (E · I)bbF bF = min

―― ·

4

―――――

1.1

(E · I)ℓ

Floor width b

The effective value of the vibration acceleration

of single­span and simply supported floors may

be calculated as follows:

0.4 · · F0 arms = ――――――――― NA.7.2­E4

2 · ξ · M*

where

arms Effective value of the vibration

acceleration, in m/s²

Fourier coefficient in dependence of the

Eigenfrequency, with = ℮ ­ 0.4 · f1

F0 Load of a person walking on the

considered floor (i. d. R.: F0 = 700 N), in N

ξ Modal damping ratio (damping ratio acc.

to Lehr) in accordance to Table 18

M* Modal mass in kg taking into account the

effective width bf in m

ℓ M* = m · ―― · bf

2

Floor vibrations may also be verified by measuring

occurring vibrations directly in the buildings.

Figure 10:

Failure modes for timber­to­timber connections

t1

a

g

b

h

c d

j

e f

k

t1

t2

t2 t1

29

The equations for determining the load­carrying

capacity of steel­to­timber connections depend

on the thickness of the steel plate t compared

to the fastener diameter d. A distinction is made

between thin (t < 0.5 · d) and thick (t ≥ d) steel

plates. Interim values may be linearly interpolated.

The basis for this differentiation is the different

support of the fastener in the steel plate. Thick

plates are considered as clamping supports, thin

plates as a hinge. Internal steel plates, regardless

of the material thickness, are considered thick

plates, since no rotation of the fasteners within

the plate is possible.

Fasteners with a withdrawal resistance lead to

higher load­carrying capacities of connections

(rope effect). For connections made of BauBuche,

the rope effect can be taken into consideration

only for screws and bolts, since other fasteners

cannot be loaded in an axial direction. The rope

effect can be described as follows: Under loading,

the fastener deforms, is inclined in the area of

the shear plane and is thus subject to axial load.

This causes the members to be pressed against

each other, while friction in the shear plane may

result in additional forces being transmitted (see

Figure 12).

This effect can be taken into consideration when

making calculations, by increasing the lateral

load­carrying capacity by a quarter of the axial

load­carrying capacity. For screws, the increase

due to the rope effect is limited to the load­carry­

ing capacity determined by the Johansen theory.

For bolts, the rope effect is limited to 25 % of the

load­carrying capacity according to Johansen.

For failure mechanisms without any inclination of

the fastener in the area of the shear plane, no

rope effect applies.

Figure 11: Failure modes for steel­to­timber connections

t1

a b c d e f

g h j/l k m

t2

6.1.1 Application and reductions for dowel-

type fasteners in Board BauBuche S/Q and

Beam BauBuche GL75

Figure 13 to Figure 15 show a schematic illustra­

tion of member surfaces where nails / screws or

bolts / dowels may be loaded in shear. In addition,

the embedding strength must be reduced de­

pending on the installation situation and direction

of loading.

The definition of the member surfaces is shown

in Figure 16.

Figure 12: Rope effect

Figure 13: Application area and reduction factors of

embedding strength for Board BauBuche S

100 %

100 %

100 %

70 %

80 %

Figure 14: Application area and reduction factors of

embedding strength for Board Bau­Buche Q

100 %

60 %

100 %

70 %

80 %

Figura 15. Application area and reduction factors of em­

bedding strength for Beam Bau­Buche GL75

100 %100 %

80 % in both

directions for d ≥ 8 mm100 %

for d ≥ 8 mm

30

Simplified method for determining the load-

carrying capacity of laterally loaded dowel-type

fasteners

As an alternative to the equations in Chapters

8.2.2 and 8.2.3, the NA­D allows a simplified

method to calculate the load­carrying capacity

of connections with laterally loaded dowel­type

fasteners. Here, the load­carrying capacity for the

failure modes with two plastic hinges per shear

plane (cases f, k for timber­to­timber connections

and cases e, h, m for steel­to­timber connections)

are calculated.*

Accordingly, to force failure modes with two

plastic hinges, pure embedding failure modes

need to be avoided. The ratio of the timber

thickness and dowel diameter must be large.

This is achieved by defining minimum timber

thicknesses treq. Failure to comply with these

minimum timber thicknesses means the load­

carrying capacity needs to be reduced with the

smaller ratio of t1/t1,req and t2/t2,req. The load­

carrying capacities determined using this

approach are lower than the values determined

with the precise method. As far as compliance of

treq is concerned, there is no difference between

the precise and simplified methods.

Note that in accordance with (NA.113), the design

value of the load­carrying capacity is determined

with the partial factor γM = 1.1

* For connections with external thin steel plates, the

failure mechanism with a plastic hinge (b and k) is

examined, since the hinged support in the thin plate

means a maximum of one plastic hinge per shear plane

can be formed.

Timber-to-timber connections

The characteristic value of the load­carrying

capacity Fv,Rk per shear plane and per fastener is

calculated as

2 · βFv,Rk = ―――― · 2 · My,Rk · fh,1,k · d (NA.109)

1 + β

The minimum timber thicknesses for single­shear

connections in this case amount to

β My,Rkt1,req = 1.15 · 2 · ――― + 2 · ――――― (NA.110)

1 + β fh,1,k · d

1 My,Rkt2,req = 1.15 · 2 · ――― + 2 · ――――― (NA.111)

1 + β fh,2,k · d

For double­shear connections, the following

applies for timber middle members

4 My,Rkt2,req = 1.15 · ―――― · ―――――― (NA.112)

1 + β fh,2,k · d

where

fh,2,k Ratio value ofβ = ――――

fh,1,k embedding strengths

When going below the minimum timber thick­

nesses,

t1 t2 2 · βFv,Rk = min ―――;――― · ――― · 2 · My,Rk · fh,1,k · d

t1,req t2,req 1 + β

Steel-to-timber connections

Internal and external thick steel plates:

Fv,Rk = 2 · 2 · My,Rk · fh,k · d (NA.115)

where

My,Rktreq = 1.15 · 4 · ――――― (NA.116)

fh,k · d

External thin steel plates:

Fv,Rk = 2 · My,Rk · fh,k · d (NA.117)

Minimum timber thicknesses for middle members

with fasteners in double­shear:

My,Rktreq = 1.15 · 2 2 · ――――― (NA.118)

fh,k · d

or for all other cases:

My,Rktreq = 1.15 · 2 + 2 · ――――― (NA.119)

fh,k · d

If going below the minimum timber thicknesses

FV,Rk must be reduced using

t1 t2min ――――;――――

t1,req t2,req

Figura 16. Definition of the member surfaces

end grain

surface

narrow surface

wide surface

31

6.2 Nailed connections

The following sections are based on regulations

given in EN 1995­1­1 and the technical assessment

documents of BauBuche. Deviating regulations

are possible if they are explicitly described in

technical assessment documents of fasteners.

For instance, in accordance with ETA­13/0523,

round nails with a profiled shank may be inserted

without predrilling in a steel­to­timber connection

and an axial capacity may be taken into account

if the maximum penetration depth in BauBuche is

not exceeding 34 mm.

6.2.1 Laterally loaded nails

6.2.1.1 Design

The thickness t2 of the member with the nail tip

is limited by the penetration depth in member 2.

Due to the high density (ρk > 500 kg/m3), nail

holes must be predrilled in BauBuche. Here, the

borehole diameter should be 0.8 · d.

Normally, round nails with a smooth or profiled

shank (special or anchor nails) are used. The yield

moment in this case is calculated as follows

My,Rk = 0.3 · fu · d2.6 (8.14)

The nails must be manufactured from wire with a

minimum tensile strength of 600 N/mm2.

For predrilled nail holes, the embedding strength

does not depend on the angle between the force

and grain direction

fh,k = 0.082 · (1 ­ 0.01 · d) · ρk (8.16)

Nailed joints in the end grain surfaces of

BauBuche are not permissible. For connections

in the narrow surfaces of Board BauBuche Q,

based on the current declaration of performance,

the embedding strength should be reduced

by 60 %. In accordance with ETA­14/0354 for

connections in the narrow surfaces of Beam

BauBuche GL75, the embedding strength for

diameters d ≥ 8 mm is to be reduced to 80 %.

Nails, which penetrate the narrow surfaces of

Board BauBuche S, must have a minimum

diameter of 3.1 mm.

When using nails with diameters exceeding 8 mm,

the embedding strength must be calculated as for

bolts / dowels.

For the load­carrying capacity parallel to grain of

connections with multiple nails arranged in line

parallel to grain, an effective number of fasteners

nef must be taken into account in accordance

with (8.17). The reason for this is the increased

risk of timber splitting. For connections in the

wide surfaces of Board BauBuche Q there is no

splitting risk, meaning nef = n may be assumed.

nef = nkef (8.17)

To avoid any reduction in accordance with (8.17),

the nails must be staggered by at least 1 · d

perpendicular to the grain.

6.2.1.2 Installation

Smooth­shank nails must penetrate at least 8 · d

into member 2, profiled nails at least 6 · d.

To guarantee the full load­carrying capacity of

the individual fastener, the spacing and distances

in accordance with Figure 17 and Table 26 must

be complied with. The details apply both when

attaching fasteners in the wide as well as in the

narrow surface. is the angle between the force

and the grain direction.

Table 25: Coefficient kef for predrilled nail holes

Figure 17:

Definition of

fastener spacing

and distances

Nail spacing* kef

a1 ≥ 14 · d 1.0

a1 = 10 · d 0.85

a1 = 7 · d 0.7

a1 = 4 · d 0.5

a3,t

a1

a3,ca4,c a2 a4,t

* for interim values,

linear interpolation

is possible

Spacing and distances Minimum values

Spacing a1 (parallel to the grain) (4 + | cos | ) · d 1)

Spacing a2 (perpendicular to the grain) (3 + | sin | ) · d 1)

Distance a3,t (loaded end) (7 + 5 · cos ) · d

Distance a3,c (unloaded end) 7 · d

Distance a4,t (loaded edge) d < 5 mm: (3 + 2 · sin ) · d

d ≥ 5 mm: (3 + 4 · sin ) · d

Distance a4,c (unloaded edge) 3 · d

Note: Board BauBuche Q may be considered as panel. Reducing a1

and a2 by the factor 0.85 is thus permissible.

Table 26: Minimum spacing and distances according to

Figure 17 for nails in predrilled holes

1) The minimum spacings a1 and a2 may be reduced for

panel­to­timber connections by the factor 0.85 and for

steel­to­timber connections by the factor 0.7.

32

Example 12: Steel-to-timber nailed connec-

tion in Board BauBuche

What we consider here is a single­shear steel­

to­timber connection. The steel plate thickness is

t = 5 mm. Two rows with three nails 6 x 60 mm

per row are selected.

According to Chapter 6.1, thick and thin steel

plates must be distinguished:

– Thin steel plate: t < 0.5 · d = 3 mm

– Thick steel plate: t ≥ d = 6 mm

The selected steel plate is between both limit

values. Linear interpolation between the design

values for thick and thin steel plates is used to

determine the load­carrying capacity.

According to Table 27, the embedding strength

is fh,k = 56.3 N/mm2 and the yield moment

My,Rk = 19,000 Nmm. The thickness of the timber

member is 80 mm, kmod = 0.8 is taken into consi­

deration.

Load­carrying capacity of a connection with a

thin steel plate:

0.4 · fh,k · t1 · d (a)Fv,Rk = min

1.15 · 2 · My,Rk · fh,k · d (b)

0.4 · 56.3 · 55 · 6 = min (8.9)

1.15 · 2 · 19,000 · 56.3 · 6

7,400 N = min = 4.1 kN

4,100 N

Load­carrying capacity of a connection with a

thick steel plate:

fh,k · t1 · d (c) 4 · My,Rk fh,k · t1 · d · 2 + ――――――― ­ 1 (d)

Fv,Rk = min fh,k · d · t2

1

2.3 · My,Rk · fh,k · d (e)

56.3 · 55 · 6 4 · 19,000 56.3 · 55 · 6 ·

2 + ―――――――― ­ 1

= min 56.3 · 6 · 552

2.3 · 19,000 · 56.3 · 6

18,500 N

= min 8,100 N = 5.8 kN (8.10)

5,800 N

Interpolating between the governing characteris­

tic values of the load­carrying capacity reveals

Fv,Rk = 4.1 kN + 2 / 3 · (5.8 kN ­ 4.1 kN) = 5.2 kN

Table 27: Yield moment My,Rk and embedding strength

fh,0,k for nailed joints (where fu = 600 N/mm²) in BauBuche

with ρk = 730 kg/m3

Table 28: Load­carrying capacity Fv,Rk per shear plane in accordance with (NA.109) and minimum wood thicknesses treq of timber­to­timber

connections with nails (BauBuche; nails in wide surface; ρk = 730 kg/m3)

d in mm 2.7 3.0 3.4 3.8 4.0 4.2 4.6 5.0 5.1 5.5 6.0 7.0 8.0

My,Rk in N mm 2,380 3,130 4,340 5,790 6,620 7,510 9,520 11,800 12,400 15,100 19,000 28,400 40,100

fh,k in N/mm2 58.2 58.1 57.8 57.6 57.5 57.3 57.1 56.9 56.8 56.6 56.3 55.7 55.1

d in mm 2.7 3.0 3.4 3.8 4.0 4.2 4.6 5.0 5.1 5.5 6.0 7.0 8.0

Fv,Rk in kN 0,87 1,04 1,31 1,59 1,74 1,90 2,24 2,59 2,68 3,07 3,58 4,70 5,94

treq (single­shear) in mm 15,3 16,6 18,4 20,2 21,1 21,9 23,6 25,3 25,7 27,4 29,4 33,5 37,5

treq (double­shear) in mm 12,7 13,8 15,3 16,7 17,5 18,2 19,6 21,0 21,3 22,7 24,4 27,7 31,0

F

t1 t

6.2.2 Axially loaded nails

Smooth­shank nails in predrilled holes may not

be subject to withdrawal.

33

and the design value of the overall load­carrying

capacity of the connection:

0.8Fv,Rd = ――― · 5.2 kN · 6 = 19.2 kN

1.3

Note: nef = n, since a staggered nail configuration,

the use of Board BauBuche Q or a sufficiently

large spacing a1 is assumed.

6.3 Stapled connections

Connections in BauBuche with staples are not

permissible, in accordance with the declaration of

performance.

6.4 Bolted and dowelled connections

6.4.1 Laterally loaded bolts or dowels

6.4.1.1 Design

For dowels and bolts the yield moment is

My,Rk = 0.3 · fu,k · d2.6 (8.30)

where tensile strength fu,k according to

Table 29 and Table 30.

For connections in the narrow surfaces of Board

BauBuche, the embedding strength in accordance

with the current declaration of per formance is

to be reduced to 70 % for in­plane loads and to

80 % for loads perpendicular to the panel plane.

Interim values may be linearly interpolated.

For connections in the narrow surfaces of Beam

BauBuche GL75, the embedding strength is

reduced to 80 % in accordance with ETA­14/0354

for diameters d ≥ 8 mm.

For the load­carrying capacity parallel to grain

of connections with multiple fasteners arranged

in line parallel to grain, an effective number of

fasteners nef must be taken into account in accor­

dance with (8.34). The reason for this is the in­

creased risk of the timber splitting. Connections

in the wide surfaces of Board BauBuche Q are

not subject to any splitting risk, meaning nef = n

may be assumed.

a1nef = min n ; n0.9 · 4 ―――― (8.34)

13 · d

The yield moments of different fastener types are

specified in Table 33.

The embedding strength for diameters up to

30 mm is:

0.082 · (1 ­ 0.01 · d) · ρkfh, ,k = ―――――――――――――――― (8.31); (8.32)

k90 · sin2 + cos2

where k90 = 0.90 + 0.015 · d in accordance with

(8.33) for members made of BauBuche.

The values for the embedding strength in Bau Buche

with a characteristic value of the den sity of

730 kg/m3 can be taken from Table 34.

Fasteners inserted parallel to the grain in the end

grain surface of BauBuche are not permissible.

Table 29: Tensile strength fu,k for bolts

Table 30: Tensile strength fu,k for dowels

Strength class fu,k in N/mm2

4.6 400

5.6 500

8.8 800

10.9 1,000

Steel grade fu,k in N/mm2

S235 360

S275 430

S355 490

In Table 35, values for nef are specified depending

on the fastener diameter and the spacing.

For between load and fibre direction of the wide

surface of 0° to 90°, linear interpolation between

n and nef is possible.

Inserting fully threaded screws as transverse rein­

forcement eliminates the need to reduce the num­

ber of fasteners. The screws should be arranged

on the loaded side of the bolts / dowels and should

be designed for axial loading equating 30 % of the

lateral load of the bolts / dowel.

Example 13: Steel-to-timber connection with

internal steel plate

Input parameters Beam BauBuche GL75

160/200 mm

service class 1, kmod = 0.9

Thickness of

the steel plate t = 12 mm

Spacing a1 = 60 mm, a2 = a4,c = 50 mm

a3,t

F

F1F1F1

F1

a1

a2

a4,c

34

fh,1,k · t1 · d 4 · My,Rk fh,1,k · t1 · d · 2 + ―――――――― ­ 1

Fv,Rk = min fh,1,k · d · t2

1

2.3 · My,Rk · fh,1,k · d

42.2 · 74 · 12 4 · 69,100 42.2 · 74 · 12 ·

2 + ―――――――― ­ 1

= min 42.2 · 12 · 742

2.3 · 69,100 · 42.2 · 12

37,400 N (f)

= min 16,800 N (g) = 13.6 kN

13,600 N (h)

The governing failure mode is two plastic hinges

per shear plane (Johansen case h).

For multiple dowels parallel to grain, the overall

load­carrying capacity taking into consideration

the effective number of fasteners nef must be

calculated. According to Table 35 nef = 2.74.

Accordingly, this leads to the overall load­carrying

capacity

2.74 0.9Fv,Rd = 2 · 12 · ――― · ――― · 13.6 kN = 155 kN

4 1.3

If a reinforcement to eliminate the splitting risk

is used (fully threaded screws), nef = n can be

assumed. This means a significant increase in the

overall load­carrying capacity of the connection

0.9Fv,Rd = 2 · 12 · ――― · 13.6 kN = 226 kN

1.3

In both timber side members, for each dowel row,

a fully threaded screw (d = 6 mm) is screwed in.

The screws must be designed for 30 % of the lat­

eral load acting on the dowels.

With the simplified design method, the load­

carry ing capacity per fastener and shear plane

can be determined as follows:

Fv,Rk = 2 · 2 · My,Rk · fh,k · d

= 2 · 2 · 69,100 · 42.2 · 12 = 11.8 kN

where

My,Rktreq = 1.15 · 4 · ――――――

fh,k · d

69,100 = 1.15 · 4 · ―――――― = 53.8 mm ≤ tvorh = 74 mm

42.2 · 12

The overall load­carrying capacity for the con­

nection, taking into consideration the effective

number of fasteners nef is

2.74 0.9Fv,Rd = 2 · 12 · ――― · ――― · 11.8 kN = 159 kN

4 1.1

and for the connection reinforced against splitting

0.9Fv,Rd = 2 · 12 · ――― · 11.8 kN = 232 kN

1.1

Version 2: 12 bolts (M12 – 4.6) with washer 44/4

According to Table 33, the yield moment for bolts

(4.6) with the diameter 12 mm is:

My,Rk = 76,700 Nmm

The load­carrying capacity per shear plane is in

accordance with (8.11)

fh,1,k · t1 · d 4 · My,Rk fh,1,k · t1 · d

· 2 + ―――――――― ­ 1

Fv,Rk = min fh,1,k · d · t1

2

2.3 · My,Rk · fh,1,k · d

42.2 · 74 · 12 4 · 76,700 42.2 · 74 · 12 ·

2 + ―――――――― ­ 1

= min 42.2 · 12 · 742

2.3 · 76,700 · 42.2 · 12

Version 1: 12 dowels (S235, d = 12 mm)

The dowels are inserted into the narrow surfaces

of the Beam BauBuche GL75. The load direction is

parallel to grain. The embedding strength accord­

ing to Table 34 must therefore be reduced to 80 %

according to ETA­14/0354.

fh,1,k = 0.8 · 52.7 N/mm2 = 42.2 N/mm2

According to Table 33, the yield moment for

dowels (S235) with the diameter of 12 mm is

My,Rk = 69,100 Nmm

The load­carrying capacity per shear plane is in

accordance with (8.11)

F1,k ≥ 0.3 · Fv,Rk = 0.3 · 13.6 kN = 4.08 kN

The minimum penetration length ℓef of the screws

corresponds to the edge distance a4,c = 50 mm.

According to Table 45, the withdrawal capacity is

Fax,Rk = 10.5 kN. The selected screws are thus suf­

ficient.

35

37,400 N (f)

= min 17,000 N (g) = 14.3 kN

14,300 N (h)

The lateral load­carrying capacity may be in­

creased due to the rope effect. The characteristic

compressive capacity under the washer according

to Table 32 is 57.9 kN. The design value of

the axial load­carrying capacity Ft,Rd is 24.3 kN

(see Table 31). For ease of calculation, this value

is converted to a characteristic value. For this

purpose, the value is multiplied with the ratio

γM / kmod : 24.3 · 1.3 / 0.9 = 35.1 kN. The increase

from the rope effect may be applied at Fax,k/4,

but not exceeding 25 % of Fv,Rk (governing here).

5Fv,Rk = ―― · 14.3 = 17.9 kN

4

Taking into consideration the effective number

of fasteners nef, the total load­carrying capacity

Fv,Rd of the connection can be found:

2.74 0.9Fv,Rd = 2 · 12 · ――― · ――― · 17.9 kN = 204 kN

4 1.3

Using a suitable reinforcement (as in the earlier

example), the full number of fasteners is effective:

0.9Fv,Rd = 2 · 12 · ――― · 17.9 kN = 297 kN

1.3

Depending on the bolt grade, the load­carrying

capacity of the connection, primarily due to the

rope effect, can be increased by around 30 %

relative to the version with dowels.

6.4.1.2 Installation

The minimum spacing and distances in accor­

dance with Table 36 must be complied with.

For tight­fitting bolts and dowels, the boreholes

must be drilled equivalent to the fastener dia­

meter. For bolts, the borehole may be drilled a

maximum of 1 mm larger. For holes in steel plates,

a tolerance of 1 mm is also permissible. External

steel plates must not be used with dowels.

It is recommended to install at least two fasteners

or four shear planes per connection. Connections

with only one fastener should only be taken into

account with 50 % of the load­carrying capacity.

6.4.2 Axially loaded bolts

For bolts, the resistance in the axial direction

(withdrawal) is the minimum of the compressive

capacity under the washer and the tensile capaci­

ty ft,Rd of the bolts. Unlike spruce, the high com­

pressive strength perpendicular to the grain of

BauBuche means steel failure may be governing.

The compressive capacity under the washer is

calculated from the effective contact area and

three times the value of the compressive strength

perpendicular to the grain fc,90,k, see Table 32.

Dowels cannot transfer forces in axial direction.

Table 31: Design value of the steel tensile capacity Ft,Rd

of bolts in kN

Table 32: Characteristic compressive capacity in kN

under washers depending on fc,90,k

* may be multiplied by 1.2 in service class 1

Strength class

d in mm 4.6 5.6 8.8 10.9

12 24.3 30.3 48.6 60.7

16 45.2 56.5 90.4 113

20 70.6 88.2 141 176

24 102 127 203 254

Bolts Washer fc,90,k in N/mm2

d in mm Type 10.0* 12.3* 14.0 16.0*

12 44/4 41.3* 50.8* 57.9 66.1*

58/6 74.6* 91.8* 104,5 119.4*

16 56/5 66.7* 82.0* 93.3 106.7*

68/6 101.3* 124.6* 141.8 162.1*

20 72/6 110.7* 136.2* 155.0 177.2*

80/8 139.4* 171.5* 195.1 223.0*

24 85/6 154.3* 189.8* 216.0 246.9*

105/8 242.6* 298.4* 339.6 388.2*

Table 33: Yield

moment My,Rk

for dowels and

bolts in Nmm

Steel grade Diameter d in mm

6 8 10 12 16 20 24 30

4.6 12,700 26,700 47,800 76,700 162,000 290,000 465,000 831,000

5.6 15,800 33,400 59,700 95,900 203,000 362,000 582,000 1,040,000

8.8 25,300 53,500 95,500 153,000 324,000 579,000 931,000 1,660,000

10.9 31,600 66,900 119,000 192,000 405,000 724,000 1,160,000 2,080,000

S235 11,400 24,100 43,000 69,100 146,000 261,000 419,000 748,000

S275 13,600 28,700 51,400 82,500 174,000 311,000 500,000 894,000

S355 15,500 32,800 58,500 94,000 199,000 355,000 570,000 1,020,000

36

Spacing and distances Minimum values Minimum values

Bolts Tight­fitting bolts / dowels

Spacing a1

(parallel to the grain) 0° ≤ ≤ 360° (4 + | cos |) · d (3 + 2 · | cos |) · d

Spacing a2

(perpendicular to the grain) 0° ≤ ≤ 360° 4 · d 3 · d

Distance a3,t

(loaded end) ­90° ≤ ≤ 90° max (7 · d ; 80 mm) max (7 · d ; 80 mm)

Distance a3,c

(unloaded end) 90° ≤ < 150° (1 + 6 · sin ) · d max [(a3,t · | sin |) ; 3 · d]

150° ≤ < 210° 4 · d 3 · d

210° ≤ ≤ 270° (1 + 6 · sin ) · d max [(a3,t · | sin |) ; 3 · d]

Distance a4,t

(loaded edge) 0° ≤ ≤ 180° max [(2 + 2 · | sin |) · d ; 3 · d] max [(2 + 2 · sin ) · d ; 3 · d]

Distance a4,c

(unloaded edge) 180° ≤ ≤ 360° 3 · d 3 · d

Table 34:

Embedding

strength fh, ,k

for dowels and

bolts in N/mm2

in the wide

surface of

BauBuche with

ρk = 730 kg/m3

Table 35: Effec­

tive number nef

for multiple do­

wels and bolts

arranged paral­

lel to the grain

Table 36: Mini­

mum spacing

and distances

according to

Figure 17 for

bolts, tight­fit­

ting bolts and

dowels

Number n Spacing a1 as a multiple of the diameter d

5 · d 6 · d 7 · d 8 · d 10 · d 12 · d 14 · d 16 · d 18 · d 20 · d 24 · d 28 · d

2 1.47 1.54 1.60 1.65 1.75 1.83 1.90 1.97 2.00 2.00 2.00 2.00

3 2.12 2.22 2.30 2.38 2.52 2.63 2.74 2.83 2.92 2.99 3.00 3.00

4 2.74 2.87 2.98 3.08 3.26 3.41 3.55 3.67 3.78 3.88 4.00 4.00

5 3.35 3.51 3.65 3.77 3.99 4.17 4.34 4.48 4.62 4.74 4.96 5.00

6 3.95 4.13 4.30 4.44 4.70 4.92 5.11 5.28 5.44 5.59 5.85 6.00

7 4.54 4.75 4.94 5.10 5.40 5.65 5.87 6.07 6.25 6.42 6.72 6.98

8 5.12 5.36 5.57 5.76 6.09 6.37 6.62 6.84 7.05 7.24 7.57 7.87

10 6.26 6.55 6.80 7.04 7.44 7.79 8.09 8.37 8.62 8.85 9.26 9.62

12 7.37 7.71 8.02 8.29 8.77 9.17 9.53 9.86 10.2 10.4 10.9 11.3

14 8.47 8.86 9.21 9.52 10.1 10.5 11.0 11.3 11.7 12.0 12.5 13.0

16 9.55 9.99 10.4 10.7 11.4 11.9 12.4 12.8 13.2 13.5 14.1 14.7

Diameter d in mm

6 8 10 12 16 20 24 30

0° 56.3 55.1 53.9 52.7 50.3 47.9 45.5 41.9

15° 56.3 55.1 53.7 52.4 49.8 47.3 44.7 40.9

30° 56.3 55.1 53.2 51.6 48.6 45.6 42.7 38.5

45° 56.3 55.1 52.6 50.7 47.0 43.5 40.3 35.7

60° 56.3 55.1 51.9 49.7 45.5 41.6 38.1 33.2

75° 56.3 55.1 51.5 49.0 44.5 40.4 36.6 31.6

90° 56.3 55.1 51.3 48.8 44.1 39.9 36.1 31.0

37

Table 37: Load­carrying capacity Fv,Rk per shear plane in accordance with (NA.109) in kN and minimum timber thicknesses treq in mm

of bolts and dowels in timber­to­timber connections (wide surfaces; ρk = 730 kg/m3)

Table 39: Load­carrying capacity

Fv,Rk per shear plane in accordance

with (NA.117) in kN and minimum

timber thicknesses treq in mm of

bolts and dowels in steel­to­timber

connections with external thin

steel plates (wide surfaces;

ρk = 730 kg/m3)

d 12 16 20 24

0° 90° 0° 90° 0° 90° 0° 90°

Strength class 4.6 Fv,Rk 13.9 13.4 22.8 21.4 33.3 30.4 45.1 40.2

treq 50.7 52.7 65.3 69.7 80.0 87.6 95.0 106.6

Strength class 8.8 Fv,Rk 19.7 19.0 32.3 30.3 47.1 43.0 63.8 56.8

treq 71.7 74.5 92.4 98.6 113.1 123.9 134.3 150.7

Steel grade S235 Fv,Rk 13.2 12.7 21.7 20.3 31.6 28.8 42.8 38.1

treq 48.1 50.0 62.0 66.1 75.9 83.1 90.1 101.1

d 12 16 20 24

0° 90° 0° 90° 0° 90° 0° 90°

Strength class 4.6 Fv,Rk 9.85 9.48 16.15 15.13 23.5 21.5 31.9 28.4

Double­shear treq 35.8 37.2 46.2 49.3 56.6 62.0 67.1 75.4

Single­shear treq 43.3 45.0 55.7 59.5 68.3 74.8 81.1 91.0

Strength class 8.8 Fv,Rk 13.9 13.4 22.8 21.4 33.3 30.4 45.1 40.2

Double­shear treq 50.7 52.7 65.3 69.7 80.0 87.6 95.0 107

Single­shear treq 61.2 63.6 78.8 84.2 96.6 106 115 129

Steel grade S235 Fv,Rk 9.34 8.99 15.3 14.4 22.3 20.4 30.2 26.9

Double­shear treq 34.0 35.3 43.8 46.8 53.7 58.8 63.7 71.5

Single­shear treq 41.0 42.7 52.9 56.5 64.8 71.0 76.9 86.3

Table 38: Load­carrying capacity

Fv,Rk per shear plane in accordance

with (NA.115) in kN and minimum

timber thicknesses treq in mm of

bolts and dowels in steel­to­timber

connections with internal and

external thick steel plates (wide

surfaces; ρk = 730 kg/m3)

d in mm 12 16 20 24

0° 90°

0° 90° 0° 90°

0° 90° 0° 90°

0° 90° 0° 90°

0° 90°

­ 90° ­ 0° ­ 90° ­ 0° ­ 90° ­ 0° ­ 90° ­ 0°

β 1.00 1.00 0.68 1.48 1.00 1.00 0.65 1.54 1.00 1.00 0.63 1.60 1.00 1.00 0.60 1.66

Strength class 4.6

Fv,Rk 9.85 9.48 9.66 9.66 16.2 15.1 15.6 15.6 23.6 21.5 22.5 22.5 31.9 28.4 30.0 30.0

Single­shear

t1,req 43.3 45.0

42.9 45.3 55.7 59.5

55.0 60.3 68.3 74.8

67.0 76.2 43.3 45.0

42.9 45.3

t2,req 45.3 42.9 60.3 55.0 76.2 67.0 45.3 42.9

Double­shear

t2,req 35.8 37.2 38.0 35.1 46.2 49.3 50.9 44.6 56.6 62.0 64.7 53.9 35.8 37.2 38.0 35.1

Strength class 8.8

Fv,Rk 13.9 13.4 13.7 13.7 22.8 21.4 22.1 22.1 33.3 30.4 31.8 31.8 45.1 40.2 42.4 42.4

Single­shear

t1,req 61.2 63.6

60.7 64.1 78.8 84.2

77.7 85.3 96.6 105.8

94.7 107.7 61.2 63.6

60.7 64.1

t2,req 64.1 60.7 85.3 77.7 107.7 94.7 64.1 60.7

Double­shear

t2,req 50.7 52.7 53.7 49.7 65.3 69.7 72.0 63.1 80.0 87.6 91.5 76.3 50.7 52.7 53.7 49.7

Steel grade S235

Fv,Rk 9.34 8.99 9.16 9.16 15.3 14.4 14.8 14.8 22.3 20.4 21.3 21.3 30.2 26.9 28.4 28.4

Single­shear

t1,req 41.0 42.7

40.7 43.0 52.9 56.5

52.2 57.2 64.8 71.0

63.5 72.3 41.0 42.7

40.7 43.0

t2,req 43.0 40.7 57.2 52.2 72.3 63.5 43.0 40.7

Double­shear

t2,req 34.0 35.3 36.0 33.3 43.8 46.8 48.3 42.3 53.7 58.8 61.4 51.2 34.0 35.3 36.0 33.3

38

6.5 Screwed connections

6.5.1 General points

For this chapter, the values of screws in accor­

dance with ETA­11/0190 as of 23.07.2018 (Würth

Assy) and ETA­12/0373 as of 03.11.2017 (Schmid

RAPID Hardwood) are used for examples. In

general, all screws may be used for connections

in BauBuche, if their approval/ETA includes the

use in laminated veneer lumber made of beech

in accordance with EN 14374. Generally, screws

in predrilled holes are used (see Table 44). Screws

with drilling tips are not a substitute for predrilling.

From a legislative point of view, the requirements

given in the assessment documents concerning

predrilling diameters are binding. Extensive inves­

tigations carried out by the Technical University of

Graz have shown that a predrilling diameter of up

to 0.8∙d does not have a significant influence on

the withdrawal capacity of a self­drillling screw

with a current thread shape inserted in BauBuche.

Resulting larger predrilling diameters are already

included in ETA­12/0197 as of 28.02.2019. Please

contact the company Pollmeier for further infor­

mation.

Further information concerning screws, whose

assessment documents allow for insertion

without predrilling, can be found in brochure 05

“Fasteners”.

6.5.2 Laterally loaded screws

6.5.2.1 Design acc. to ETA-11/0190

The embedding strength of Würth screws in pre­

drilled and non­predrilled members is calculated

as for nails:

0,082 · pk · d­0,15

fh,k = ―――――――――――――――――――

(2,5 · cos2 + sin2 ) · kξ · kβ

d Nominal diameter of the screw

ρk = 730 kg/m³ Characteristic density of

BauBuche

Angle between screw axis and fibre direction

kε =(0.5 + 0.024 · d) · sin2 ε + cos2 ε

ε Angle between load and fibre direction and

kβ = 1.2 · cos2 β + sin2 β

β Angle between screw axis and wide surface

.It is important to note that screws, which are

inclined in the direction of loading, are mainly

subject to axial stresses and are thus designed

in accordance with Chapter 6.5.2.

The values of the yield moments can be taken

from the approvals of the screws or estimated as

My,Rk = 0.15 · fu,k · d2.6

Screws made of carbon steel generally have a

nominal tensile strength fu,k of 600 N/mm2,

while the strength of stainless steel screws is

400 N/mm2.

If the effective number of multiple screws arranged

parallel to the grain shall equal the actual number,

screws must be arranged in a staggered configu­

ration, at least 1 · d perpendicular to the grain rela­

tive to each other.

Laterally loaded screwed connections in the

end grain surfaces of BauBuche are generally not

allowed.

ETA­11/0190 considers the reduction of the em­

bedding strength of screws inserted in the end

grain surfaces through the angle . For connec­

tions with nails or screws in the narrow surfaces

of Board BauBuche Q, the embedding strength

shall be reduced to 60% in accordance with the

current declaration of performance, see Figure 14.

For connections in the narrow surfaces of Beam

BauBuche GL75, the embedding strength is

reduced by parameter β in the equation given

above. Table 40 and Table 41 give current em­

bedding strength values for screws acc. to ETA­

11/0190, which are valid for predrilled and

non­predrilled BauBuche.

The minimum diameter of laterally loaded screws

inserted in the narrow surfaces of Board Bau­

Buche S is 6.0 mm.

Table 40: Yield moment My,Rk and embedding strength

fh, ,k for carbon steel screws in accordance with

ETA­11/0190 in narrow surface of BauBuche with ρk =

730 kg/m3 (β = 0° und = 90°)

Diameter d in mm

5 6 8 10 12

My,Rk

in Nmm 5,900 10,000 23,000 36,000 58,000

ε fh,ε,k in N/mm2

0° 39.2 38.1 36.5 35.3 34.4

15° 40.2 39.1 37.3 35.9 34.9

30° 43.3 41.9 39.6 37.8 36.3

45° 48.4 46.4 43.2 40.6 38.4

60° 54.8 52.0 47.5 43.9 40.9

75° 60.7 57.1 51.2 46.6 42.8

90° 63.2 59.2 52.8 47.7 43.6

39

6.5.2.2 Installation

For screws inserted in predrilled BauBuche,

regardless of diameter, the minimum spacing and

distances for nailed joints (Table 26) should be

complied with.

For screws inserted in non­predrilled BauBuche,

regardless of the diameter, the minimum spacing

and distances for nailed joints in higher density

timber (Tabelle 42) should be complied with.

According to ETA­11/0190, the minimum member

thickness in accordance with Table 43 must be

complied with.

Table 43:

Minimum member thickness

tmin for screws in accordance

with ETA­11/0190

d in mm tmin in mm

< 8 24

8 30

10 40

12 80

Table 41. Yield moment My,Rk and embedding strength

fh, ,k for carbon steel screws in accordance with ETA­

11/0190 in wide surfaces of BauBuche with ρk = 730 kg/

m3 (β = 0° und = 90°)

Diameter d in mm

5 6 8 10 12

My,Rk

in Nmm 5,900 10,000 23,000 36,000 58,000

ε fh,ε,k in N/mm2

0° 47.0 45.8 43.8 42.4 41.2

15° 48.2 46.9 44.7 43.1 41.8

30° 52.0 50.2 47.5 45.3 43.5

45° 58.1 55.7 51.8 48.7 46.1

60° 65.8 62.4 57.0 52.6 49.0

75° 72.8 68.5 61.5 56.0 51.4

90° 75.8 71.0 63.3 57.3 52.3

Table 42: Minimum spacing and distances according to

Figure 17 for screws in non­predrilled BauBuche in ac­

cordance with ETA­11/0190

Spacing and distances Minimum values

Spacing a1

(parallel to the grain) (7 + 8 · | cos |) · d

Spacing a2

(perpendicular to the grain) 7 · d

Distance a3,t

(loaded end) (15 + 5 · cos ) · d

Distance a3,c

(unloaded end) 15 · d

Distance a4,t d < 5 mm:

(loaded edge) (7 + 2 · sin ) · d

d ≥ 5 mm:

(7 + 5 · sin ) · d

Distance a4,c

(unloaded end) 7 · d

6.5.2 Axially loaded screws

6.5.2.1 Design

For the load­carrying capacity of connections

with axially loaded screws, the following points

must be considered:

– Withdrawal

– Head pull­through

– Tensile capacity of the screw

For screws subject to compressive loads, the

buckling of the screw should be considered rather

than the tensile load­carrying capacity.

The withdrawal resistance of a screw in accor­

dance with ETA­11/0190 in BauBuche is

nef · kax · fax,k · d · ℓefFax, ,Rk = ――――――――――――――――

kβ

with

kax = 1.0 for 45° ≤ ≤ 90° respectively

0.5 · kax = 0.5 + ――――― for 0° ≤ ≤ 45°;

45°

fax,k = 35 N/mm2 and

kβ = 1.5 · cos2 β + sin2 β

Depending on:

– Effective thread length ℓef

Length of the threaded part in the respective

member subject to withdrawal. For fully

threaded screws, minus the length of the

smooth parts at the screw tip and head.

Table 44. Predrilling diameter for screws in BauBuche

d

in mm

6

8

10

12

14

See also section 6.5.1

Predrilling di­

ameter in mm,

e.g. in accor­

dance with

ETA­11/0190

4.0

6.0

7.0

8.0

9.0

Predrilling di­

ameter in mm

in accordance

with

ETA­12/0197

4.5

6.5

8.0

9.0

11.0

40

For screws with a diameter of 8 mm, countersunk

washers 45°with dhead = 25 mm and a thickness

of at least 40 mm:

Fax, ,Rk = nef · 22,500 N

The tensile load­carrying capacity is calculated as

follows:

Ft,Rk = nef · ftens,k (8.40c)

The tensile capacity ftens,k is to be taken from the

approvals/ETA of the screws (see Table 46).

The partially threaded self­drilling screw RAPID

Hardwood of the company Schmid Schrauben

Hainfeld in accordance with ETA­12/0373 as of

03.11.2017 was developed especially for the use

in hardwood species and has high load­carrying

capacities. For instance, the head pull­through

capacity of a screw with a diameter of 8 mm and

a thread length of 100 mm is 32.1 kN. The RAPID

Hardwood screw has a high tensile capacity

ftens,k = 32.8 kN and a high yield moment My,k = 

42.8 Nm thanks to the increased core diameter.

– Outer thread diameter d

d corresponds to the nominal diameter of the

screws

– Angle between screw axis and grain direction

For screws in the wide and narrow surfaces,

corresponds to the insertion angle. In the end

grain surfaces, = 90° minus screw­in angle.

The current declaration of performance for

BauBuche limits the minimum angle to 45°,

in accordance with the screw approvals / ETA,

smaller angles would mostly be permissible.

According to ETA­11/0190, Fax, ,Rd for angles

between 45° and 90° need not be reduced.

– Angle β between screw axis and wide surface

kβ = 1.0 for screws inserted perpendicular

to the wide surface (β = 90°)

kβ = 1.5 for screws inserted perpendicular

to the narrow surface (β = 0°)

Fax, ,Rd must not be reduced for angles

between 45° and 90° in accordance with

ETA­11/0190.

– Effective number of screws nef

For connections involving interaction among

multiple screws, nef is assumed. In particular

for connections involving steel plates, nef

should be used, since a very direct transfer

of load to the individual screws takes place,

which prevents uniform load distribution

among all fasteners.

nef is in accordance with Eurocode 5

nef = n0.9 (8.41)

For tensile forces, which act at an angle of

between 30° and 60° to the screw axis, in

accordance with ETA­11/0190

nef = max n0.9 ; 0.9 · n

must be taken into account.

The head pull­through resistance of a screw is

ρk

0.8

Fax, ,Rk = nef · fhead,k · d 2h · ――― (8.40b)

350

The head pull­through parameter fhead,k must be

taken from the approvals/ETA of the screws.

For screws with washers, the washer diameter

may be used instead of the head diameter.

For screws according to ETA­11/0190 with head

diameters dh ≤ 25 mm and a thickness of at least

40 mm:

Fax, ,Rk = nef · (40 ­ 0.5 · dh) · d2h

Table 45: Withdrawal capacity Fax,Rk in kN per 10 mm

penetration depth of screws for insertion angles

between 45° and 90° in accordance with ETA­11/0190

Table 46: Yield moment My,Rk in N/mm and tensile

capacity ftens,k in kN in accordance with ETA­11/0190

Carbon steel Stainless steel

d in mm My,Rk ftens,k My,Rk ftens,k

6 9,500 11.0 5,500 7.10

8 20,000 20.0 11,000 12.0

10 36,000 32.0 20,000 18.8

12 58,000 45.0 ­ ­

Diameter d in mm

β 5 6 8 10 12

0° (in narrow

surface) 1.17 1.40 1.87 2.33 2.80

15° 1.19 1.43 1.91 2.39 2.86

30° 1.27 1.53 2.04 2.55 3.05

45° 1.40 1.68 2.24 2.80 3.36

60° 1.56 1.87 2.49 3.11 3.73

75° 1.69 2.03 2.71 3.39 4.06

90° (in wide

surface) 1.75 2.10 2.80 3.50 4.20

41

6.5.4 Combined laterally and axially loaded

screws

If screws are simultaneously loaded laterally

and axially, the verification is performed using

quadratic interaction

Fax,Ed 2 Fv,Ed 2

―――― + ―――― ≤ 1 (8.28)

Fax,Rd Fv,Rd

When installing screws in laminated veneer lum­

ber, own values are often specified in accordance

with the approval / ETA. Example minimum dis­

tances which must be complied with in accor­

dance with Figure 19 from ETA­11/0190 are listed

in Table 47. The screw spacing and distances

in this case are defined from the centre of gravity

of the thread in the respective members.

6.5.3.2 Installation

Axially loaded screws may only be used subject

to compliance with certain minimum dimensions

for the member thickness and minimum screw

spacing and distances. Since the timber con­

struction industry nowadays uses almost exclu­

sively screws according to approvals / ETA, the

minimum dimensions to be complied with should

be taken from the respective technical assess­

ment documents. These values are often lower

than those of Eurocode 5.

Figure 18: Permissible insertion angle and diameter for

screws in BauBuche in accordance with Eurocode 5 –

for screws in accordance with e.g. ETA­11/0190, more

insertion angles are possible.

Figure 19: Definition of the minimum distances for

axially loaded screws

Table 47: Minimum spacing and distances for screws in

accordance with ETA­11/0190

Screw spacing a1 parallel to grain

of the wide surface 5 · d (7 + 8 · | cos |) · d

Screw spacing a2 perpendicular

to grain of the wide surface 2.5 · d 7 · d

End distance a1,CG 5 · d (7 + 5 · | cos |) · d

Edge distance a2,CG to the wide

and narrow surfaces 3 · d 3 · d

Screw spacing for crossed

screw pairs 1.5 · d 1,5 · d

S

a1

a1

a1

a1 a2a1,CG

a1,CG

a1,CG

a1,CG a2,CG a2,CG

a2,CGa2,CGa2,CG

a2,CG

a2,CG

a2,CG

a2,CG

a2,CG

a2,CG a2,CGa2

S S

S

S

S S

S

Type Q: d ≥ 6 mm

screw inside cone

screw inside cone

Type Q: d ≥ 6 mm

screw outside cone

45°

45° 45°

Example 14:

Tensile connection

with fully threaded

screws under 45°

A steel plate (t = 10 mm) with four fully threaded

screws 8.0 x 120 mm in accordance with ETA­

11/0190 under 45° is connected to a column made

of BauBuche.

The effective thread length is calculated from the

screw length minus the length in the steel plate

ℓef = 120 mm ­ 10 · 2 = 106 mm

45°

F

a1

a2,CG

S

42

Linear interpolation, in accordance with Table 45

and considering β = 90° and = 45°, reveals a

withdrawal capacity Fax,Rk of 106/10*2.8 = 29.6 kN

per screw. According to Table 46 the tensile

capacity is ftens,k = 22.0 kN.

With kmod = 0.9, the design value of the load­

carrying capacity in the axial direction results as:

0.9 22Fax,Rd = min ――― · 29.6 ; ―――

1.3 1.3

= min { 20.5 ; 16.9 } = 16.9 kN

Head pull­through of the head is prevented by the

steel plate and is thus not relevant.

The total load­carrying capacity of the connection

should be calculated with an effective number of

inclined screws

nef = max { 40.9 ; 0.9 · 4 } = 3.6

Fax,Rd,ges = 3.6 · 16.9 kN = 60.8 kN

Taking into consideration the angle between the

load direction and the screw axis and the rope

effect, the design load­carrying capacity is

60.8 kNFRd = 1.25 · ―――――― = 53.7 kN

2

Table 48: Load­carrying capacity Fv,Rk in kN and minimum wood thicknesses treq in mm of screws in accordance with ETA­11/0190 in

timber­to­timber and steel­to­timber connections with external steel plates; screws are inserted perpendicular to the wide surfaces and

the rope effect is not considered.

d 6 8 10 12

ε 0° 90° 0°­90° 90°­0° 0° 90° 0°­90° 90°­0° 0° 90° 0°­90° 90°­0° 0° 90° 0°­90° 90°­0°

β 1.00 1.00 1.55 0.65 1.00 1.00 1.45 0.69 1.00 1.00 1.35 0.74 1.00 1.00 1.27 0.79

Timber­to­timber connection

FV,Rk 2.34 2.92 2.58 2.58 4.01 4.83 4.36 4.36 5.53 6.42 5.92 5.92 7.57 8.53 8.01 8.01

Single­shear

t1,req 23.7 19.0

24.7 18.1 31.8 26.5

33.0 25.4 36.2 31.1

37.3 30.1 42.5 37.7

43.5 36.8

t2,req 18.1 24.7 25.4 33.0 30.1 37.3 36.8 34.5

Double­shear

t2,req 19.6 15.8 14.0 21.6 26.3 21.9 19.8 28.7 30.0 25.8 23.8 32.1 35.2 31.3 29.4 37.3

Steel­to­timber connection (thin steel plates)

FV,Rk 2.34 2.92 ­ ­ 4.01 4.83 ­ ­ 5.53 6.42 ­ ­ 7.57 8.53 ­ ­

treq 23.7 19.0 ­ ­ 31.8 26.5 ­ ­ 36.2 31.1 ­ ­ 42.5 37.7 ­ ­

Steel­to­timber connection (thick steel plates)

FV,Rk 3.32 4.13 ­ ­ 5.68 6.83 ­ ­ 7.81 9.08 ­ ­ 10.7 12.1 ­ ­

treq 27.7 22.3 ­ ­ 37.3 31.0 ­ ­ 42.4 36.5 ­ ­ 49.8 44.2 ­ ­

43

Note: In accordance with the “German general

construction technique permit (Allgemeine Bau art­

genehmigung)” no. Z­9.1­838, Boards BauBuche S

may be used as webs and Boards BauBuche Q as

sheathing for glued thin­flanged beams (stressed

skin panels) acc. to DIN 1052­10. Boards BauBuche

may be used for further glued applications acc.

to DIN 1052­10, for instance reinforcements with

glued­on boards.

Currently, the bonding of Board BauBuche and

Beam BauBuche GL75 to glued components in

normative terms is only regulated for cases, in

which the glue line pressure is applied by screws

(see Chapter 9.2.1). Here, the thickness of the

BauBuche cross­sections to be glued together is

limited to 50 mm.

Gluing individual cross­sections of Board BauBuche

to T­beams, double T­beams or box girders allows

manufacturing sophisticated members with high

bending capacities. Box girders provide a bracing

effect due to the high torsional stiffness, which

may eliminate the need for roof bracing. Glued

composite members comprise flanges (horizontal

panels), webs (vertical panels) and glued joints.

The manufacture of glued load­bearing members

is subject to a whole series of requirements. Com­

panies executing such work must be able to pro­

cure special approvals, while the range of permis­

sible climatic conditions and the moisture content

of the members to be glued are both subject

to strict limits. Moreover, only surfaces directly

planed or sanded before the gluing are permissible.

Accordingly, glued members should be already

manufactured in the factory.

Under bending moments, it is primarily the flang­

es which absorb tensile or compressive bending

stresses. As a general rule, the flanges in com­

pression are governing the design of cross­sec­

tions. Economical cross­sections are thus those

where the cross­sections of the flanges in com­

pression are larger than those in tension. When

used as roof or floor beams, the connection with

the roof or floor panels generally provides suffi­

cient bracing against any lateral displacement of

the flanges in compression. For bottom flanges

under compression, e.g. above intermediate sup­

ports, additional bracing of the bottom flanges is

possible by crosspieces to the higher­lying brac­

ing construction.

The webs primarily transfer the shear forces. Rein­

forcement by using additionally glued­on Board

BauBuche in areas with high shear forces, e.g. at

the supports, thus may be required. In addition to

shear forces, webs are also subject to bending

stresses. For cross­sections in particular, in which

the web passes through up to the upper edge,

significant bending stresses occur in the webs.

The glued joints used to connect individual cross­

sections transfer the shear forces from the webs

into the flanges. For design purposes, the glued

connections are considered rigid, eliminating any

impact of the glued joints on overall stiffness.

The strength of the glued joints may be considered

as at least equivalent to that of the neighbouring

Board BauBuche. Accordingly, only the local shear

stresses in the BauBuche members need to be

checked. If only veneers parallel to the beam axis

are glued together (Board BauBuche S), no rolling

shear stress is exerted, meaning a shear strength

value of fv,0 can be expected.

If the assembled partial cross­sections consist of

different materials, possible impacts on the verifica­

tions in the final state due to differing deformation

behaviour (kdef) must also be taken into account.

The following section focuses on symmetrical cross­

sections made up of individual parts of BauBuche

of the same type glued together.

7 GLUED COMPONENTS

DIN EN 1995­1­1, Chap. 9

Figure 20:

Box girder

beam made of

BauBuche

b1b2

A2

A1 h10.5 h1

a1

hw h2

y

z

b1

b3

b2

A2

A3

A1 h1

a2h2 = hw

h3

0.5 h2

0.5 h1

a1

a3

0.5 h3

0.5 h2

y

z

Figure 21:

Double T­beam

made of

BauBuche

44

The effective bending stiffness (EI)ef is calculated

as a composite cross­section with infinitely stiff

joints:

3Elef = ∑ (Ei · Ii + Ei · Ai · a

2i )

i=1

The distance of the centres of gravity of the indi­

vidual cross­sections from the centre of gravity of

the overall cross­section is calculated as follows

E1 · A1 · ( h1 + h2 ) ­ E3 · A3 · ( h2 + h3 )a2 = ―――――――――――――――――――――――――

2 · ∑3

i=1Ei · Ai

h1 + h2 h2 + h3a1 = ――――― ­ a2 a3 = ――――― + a2

2 2

For cross­sections with webs covering the total

height, h1 and h3 should be used with negative

signs. It is presumed that a2 is positive and

smaller than or equal to h2 / 2.

The following verifications must be performed

at the ultimate limit state:

Verification of flanges

Centre of gravity stresses:

E1(3) · Md · a1(3)σc(t),1(3),d = ――――――――――

(El)ef

Stresses in the extreme fibres:

E1(3) · Md · (a1(3) + h1(3) /2)σm,1(3),d = ――――――――――――――――――

(El)ef

Verification of web

Stress in the extreme fibres:

E2 · Md · (a2 + h2 /2)σm,2,d = ――――――――――――――

(El)ef

Shear stress:

(E3 · A3 · a3 + 0.5 · E2 · b2 · h2) · Vd

τ2,max,d = ―――――――――――――――――――――――

b2 · (El)ef

where

h2h = ――― + a2

2

Simplified buckling verification:

h1 + h3 n · b2 · hw 1 + 0.5 · ―――― · fv,d ; hw ≤ 35b2

FV,Rd ≤ hw

h1+ h3 n·35·b2

2 1 + 0.5 · ―――― · fv,d ; 35b2 ≤ h2 ≤ 70b2 hw

(9.9)

where

hw Web height between flanges

n Number of webs

Verification of local shear stresses at the glue

lines

Vd · E1(3) · S1(3) Vd · E1(3) · A1(3) · a1(3)τk,d = ―――――――――― = ――――――――――――― ≤ fv,d

(EI)ef · n · bKF,1(3) (EI)ef · n · bKF,1(3)

where

bKF Width of glued joints

n Number of glued joints

S First moment of area based on the overall

centre of gravity

Example 15: Bonded box girder

Loads:

Moment Md = 30 kNm

Shear force Vd = 15 kN

kmod = 0.8; service class 1

Dimensions:

Individual cross­sections made of

Board BauBuche Q, panel thickness 40 mm

h2 = 120 mm; b1 = 250 mm; ℓ = 6 m

Note: The following calculations can be per­

formed without consideration of the MOE­values,

since the individual cross­sections have the

same MOE.

Ief = ∑ (Ii + Ai · a2i )

= 2 · 5.76 · 106 + 2 · 1.33 · 106 + 2 · 10,000 · 802

= 1.42 · 108 mm4

1. Verification of centre of gravity stresses in

the flanges

Md · a1(3) 30 · 106 · ± 80σc(t),1(3),d = ――――― = ―――――――― = ± 16.9 N/mm2

Ief 1.42 · 108

16.9η = ――― = 0.58 ≤ 1.0

28.9

40

40

40

250

120

45

where

kℓ · ft,0,kft,0,d = kmod · ――――――

γM

0.96 · 49 N/mm2

= 0.8 · ――――――――――― = 28.9 N/mm2

1.3

1.2 · 62.0 N/mm2

fc,0,d = 0.8 · ――――――――――― = 45.8 N/mm2

1.3

In service class 1, the characteristic value of the com­

pressive strength may be modified by the factor 1.2.

2. Verification of maximum stresses in the

flanges

Md · (a1(3) + h1(3) /2)σm,1(3),d = ―――――――――――――

Ief

30 · 106 · (80 + 40/2) = ――――――――――――― = 21.1 N/mm2

1.42 · 108

21.1η = ――― = 0.42 ≤ 1.0

49.8

where

81 N/mm2

fm,d = 0.8 · ――――――― = 49.8 N/mm2

1.3

3. Verification of maximum stress in the web

Md · h2/2 30 · 106 · 120/2σm,2,d = ―――――― = ―――――――――― = 12.7 N/mm2

Ief 1.42 · 108

12.7η = ――― = 0.35 ≤ 1.0

36.3

where

59 N/mm2

fm,d = 0.8 · ――――――― = 36.3 N/mm2

1.3

4. Verification of shear stresses in the web

τ2,max,d = (10,000 · 80 + 0.5 · 80 · (120 /2)2)

· 15 · 103 / (80 · 1.42 · 108) = 1.24 N/mm2

1.24η = ――― = 0.26 ≤ 1.0 4.80

where

7.8 N/mm2

fv,d = 0.8 · ――――――― = 4.80 N/mm2

1.3

5. Simplified buckling verification of the web

hw = 120 mm ≤ 35 · b2 = 35 · 40 = 1,400 mm

h1 + h3Fv,Rd = n · b2 · hw 1 + 0.5 · ―――――― · fv,d

hw

40 + 40 = 2 · 40 · 120 1 + 0.5 · ―――――― · 4.80 · 10­3

120

= 61.4 kN

0.5 · 15 η = ―――――― = 0.12 ≤ 1.0

61.4

6. Verification of local shear stresses at the glue line

Vd · A1(3) · a1(3) 15 · 103 · 10,000 · 80τk,d = ―――――――― = ――――――――――― = 1.05 N/mm2

Ief · n · bKF,1(3) 1.42 · 108 · 2 · 40

1.05η = ――― = 0.45 ≤ 1.0

2.34

where

3.8 N/mm2

fv,d = 0.8 · ―――――――― = 2.34 N/mm2

1.3

Note: The verification of the box girder cross­ section,

as shown in Example 15 corresponds to a box girder

floor, where the same effective flange widths are used.

The use as a floor element requires additional check of

the vibration behaviour.

Example 16:

Bonded Double T-beam

Loads:

Moment Md = 850 kNm

Shear force Vd = 170 kN

ℓ = 20 m; kmod = 0.9, service class 1

Dimensions:

Web made of Board BauBuche Q

Flanges made of Board BauBuche S

EIef = 16,800 · 7.78 · 107 + 13,200 ·3.33 ·109

+ 16,800 · 2.93 · 107 + 16,800 · 28,000 · 375.92

+ 13,200 · 40,000 ·34.12 + 16,800 · 20,800 · 469.12

= 1.92 · 1014 N/mm2

a2 = (16,800 · 2 · 80 · 180 · (­180 + 1,000)

­ 16,800 · 2 · 80 · 130 · (1,000 ­ 130))/(2 · (16,800

· 28,800 + 13,200 · 40,000 + 16,800 · 20,800))

= 34.1 mm

130

180

1,00040

80

46

­ 180 + 1,000 a1 = ―――――――― ­ 34.1 = 375.9 mm

2

1,000 ­ 130a3 = ―――――――― + 34.1 = 469.1 mm

2

Subsequently, only the governing checks are

performed. A beam sufficiently braced against

flexural and torsional buckling is presumed.

1. Verification of compressive stress in the

upper flange

16,800 · 850 · 106 · (­ 375.9)σc,1,d = ――――――――――――――――― = ­ 28.0 N/mm2

1.92 · 1014

28.0η = ――― = 0.59 ≤ 1.0

47.8

where

1.2 · 57.5 N/mm2

fc,0,d = 0.9 · ――――――――――― = 47.8 N/mm2

1.3

2. Verification of tensile stress in the bottom

flange

16,800 · 850 · 106 · 469.1σt,3,d = ―――――――――――――――― = 34.9 N/mm2

1.92 · 1014

34.9η = ――― = 0.94 ≤ 1.0

37.1

where

0.892 · 60 N/mm2

ft,0,d = 0.9 · ―――――――――――― = 37.1 N/mm2

1.3

3. Verification of maximum stress in the upper

flange

16,800 · 850 · 106 · ­ (375.9 + 180/2)σm,1,d = ――――――――――――――――――――――

1.92 · 1014

= ­ 34.7 N/mm2

34.7η = ――― = 0.67 ≤ 1.0

51.9

where

75 N/mm2

fm,d = 0.9 · ―――――――― = 51.9 N/mm2

1.3

4. Verification of maximum stress in the

bottom flange

16,800 · 850 · 106 · (469.1 + 130/2)σm,1,d = ――――――――――――――――――――――

1.92 · 1014

= 39.7 N/mm2

39.7η = ――― = 0.76 ≤ 1.0

51.9

where

75 N/mm2

fm,d = 0.9 · ―――――――― = 51.9 N/mm2

1.3

5. Verification of bending stress in the web

13,200 · 850 · 106 · (34.1 + 1,000/2)σm,2,d = ――――――――――――――――――― = 31.2 N/mm2

1.92 · 1014

31.2η = ――― = 0.88 ≤ 1.0

35.3

where

0.865 · 59 N/mm2

fm,d = 0.9 · ―――――――――――― = 35.3 N/mm2

1.3

6. Verification of shear stress in the web

τ2,max,d = (16,800 · 20,800 · 469.1

+ 0.5 · 13,200 · 40 · 534.12)

· 170 · 103 / (40 · 1.92 · 1014) = 5.30 N / mm2

where

1,000h = ―――― + 34.1 = 534.1 mm

2

5.30η = ―――― = 0.98 ≤ 1.0

5.40

where

7.8 N/mm2

fv,d = 0.9 · ―――――――― = 5.40 N/mm2

1.3

7. Simplified buckling verification of the web

hw = 1,000 mm ≤ 35 · b2 = 35 · 40 = 1,400 mm

180 + 130

FV,Rd = 1 · 40 · 1,000 1 + 0.5 · ―――――――――――

(1,000 ­ 180 ­ 130)

· 5.40 · 10­3 = 265 kN

170η = ―――― = 0.64 ≤ 1.0

265

8. Verification of local shear stresses at the

glue line to the bottom flange

170 · 103 · 16,800 · 20,800 · 469.1τk,d = ――――――――――――――――――――

1.92 · 1014 · 2 · 130

= 0.56 N/mm2

0.56η = ――― = 0.21 ≤ 1.0

2.63

where

3.8 N/mm2

fv,d = 0.9 · ―――――――― = 2.63 N/mm2

1.3

47

8.1 General

Board BauBuche Q may be used for constructing

roof, floor and wall panels that supply in­plane

stiffness and capacity.

Board BauBuche is produced in thicknesses of up

to 60 mm. Together with high shear and compres­

sive strength it is suitable for use as solid shear

walls.

Solid floors made of Board BauBuche are also

possible. However, significant deflections limit

their use beyond a span of around 3.5 m.

Accordingly, only the formation and design of

solid shear walls is presented.

8.2 Shear walls

Walls are designed to accommodate vertical

loads from the dead weight, live loads and snow

as well as horizontal bracing loads caused by

wind and earthquakes. The buckling of the wall is

generally the key factor when it comes to vertical

loads. When designing for bracing loads, above

all, there is a need to carefully examine the load

introduction, the way the individual wall elements

are connected to each other and the way the

shear forces are transferred to the foundations.

Figure 23 shows an example whereby the floor

shear forces from the floor are transferred to a

solid wall panel. For this purpose, the wall is

notched at the top for the edge member of the

floor and fixed to the same by horizontal nails

or screws. The notch is required, since laterally

loaded nails / screws in the end grain of BauBuche

are not allowed (with the exception of e.g. section

6.5.2) and inclined screws under axial loading

are not feasible due to the edge distances having

to be complied with.

Board BauBuche is produced up to 1.82 m wide. In

general, walls must therefore be assembled from

multiple individual elements. One possibility is to

design a rebate with laterally loaded nails / screws

as the connection. Further information can be

found in brochure 05 “Fasteners”.

8 SHEAR WALLS AND DIAPHRAGMS

DIN EN 1995­1­1, Chap. 9.2.3/4

Figure 22: Shear wall

Figure 23: Diaphragm

to shear wall connection

Figure 24: Element connection with a rebate

(screw d = 6 mm)

Hd

qd

h

ℓ

ℓ*

Floor diaphragm

Floor beam

Edge member

Wall

a

40

80

60

40

The shear flow in the wall panels is

Hdsv,0,d = ―――

ℓ

The tensile force at the wall ends is

Hd · h ℓZd = ――――― ­ gk · ――

ℓ* 2

ℓ* is the distance from the centre of gravity of the

hold­down to the wall end.

48

Example 17: Shear wall consisting of two

elements

Board BauBuche Q, t = 60 mm,

System see Figure 22

Loads: Hd = 60 kN, service class 1, KLED short

Dimensions: h = 2.7 m, ℓ = 3.6 m

Horizontal load: The shear flow is

60 kNsv,0,d = ――――― = 16.7 kN/m

3.6 m

For the rebate connection, screws 6 x 60 mm

in accordance with ETA­11/0190 are selected.

The individual load­carrying capacity of a screw,

in accordance with Chapter 6 is Fv,Rk = 2.34 kN.

The required screw spacing therefore is

1.62 kNe = ――――――― = 0.10 m

16.7 kN/m

The shear capacity of the wall itself is

0.9fv,0,d = ―― · 7.8 N/mm2 · 30 mm = 162 kN/ m

1.3

and the actual load is far less.

The following tensile force must be anchored at

the wall ends into the foundation

60 kN · 2.7 m 3.6 mZd = ―――――――― ­ 0.9 · 1.30 kN/m · ―――― = 44.2 kN

3.5 m 2

Conservatively, only the dead weight of the wall is

considered in this case.

Vertical stress:

According to Chapter 4.2.1, the buckling coeffi­

cient is kc,z

1 1kc,z = ―――――――――― = ――――――――――――― = 0.13

kz + k2z ­ λ

2rel,z 4.27 + 4.272 ­ 2.702

where

ℓef β · ℓ 1.0 · 2.7 · 103 mm

λz = ―― = ――――― = ―――――――――――――= 156

iz b/ 12 60 mm / 12

λz fc,0,k 156 74.4λrel,z = ―― ―――― = ――― ――――――= 3.94

π E0,05 π 11,800

kz = 0.5 · (1 + 0.1 (λrel,z ­ 0.3) + λ2rel,z)

= 0.5 · (1 + 0.1 (3.94 ­ 0.3) + 3.942) = 8.43

The vertical load capacity is thus

0.9qd = 0.063 · ――― · 74.4 N/mm2 · 60 mm = 195 kN/m

1.3

9.1 Reinforcements for tensile stresses perpendi­

cular to grain

Reinforcements of timber members are mostly

required due to the low tensile strength perpen­

dicular to the grain. Perpendicular to grain tensile

stresses occur e. g. in the connection areas of

members, at notched supports, holes and in the

apex of double tapered beams. BauBuche has

far higher perpendicular to grain tensile strength

than solid or glulam softwood. Board BauBuche Q

with cross layers possesses a perpendicular to

grain tensile strength of 16 N/mm2 (for nominal

thickness B ≤ 24 mm) or 8 N/mm2 (for nominal

thickness 27 mm ≤ B ≤ 60 mm). By using members

made of BauBuche, as an alternative to solid or

glulam softwood, it is often possible to eliminate

the need of reinforcement perpendicular to grain.

Board BauBuche is ideal for use as external rein­

forcement for solid or glulam members subject to

significant perpendicular to grain tensile stresses.

Perpendicular to grain reinforcement is not

covered in Eurocode 5. This document therefore

specifies the calculation principles of the NA ­ Ger­

many. Its applicability outside Germany should

be checked.

9.2 Types of reinforcement

In terms of reinforcement, internal and external

reinforcements are distinguished. Examples

of internal reinforcements include fully threaded

screws, glued­in rods or reinforcement bars.

External reinforcements include glued­on boards

or wood­based panels. The design of fully thread­

ed screws is covered by the screw’s approv­

al / ETA. For reinforcements subsequently applied

with glued­on boards (rehabilitation), the method

of using screws to apply the necessary gluing

pressure (“screw gluing”) can be applied.

9 REINFORCEMENTS AND REHABILITATION

DIN EN 1995­1­1/NA, NCI NA 6.8

DIN EN 1995­1­1/NA, NCI NA 11.2.3

DIN EN 1995­1­1, Annex B

DIN 1052­10

49

9.2.1 Screw gluing

When retrofitting tensile cracks perpendicular to

the grain or reinforcing subsequently installed

connections or openings after those have already

been installed, the use of hydraulic presses is

generally unfeasible, due to the confined spaces.

In this case, it is possible to manufacture load­

bearing glued connections using “screw gluing”.

In the process, the pressure is applied by self­

drilling partially threaded screws. Eurocode 5

does not cover screw gluing. Accordingly,

reference is made at this point to DIN 1052­10.

To ensure uniform pressure and thus ensure the

quality of the glued joints, the thickness of the

wood­based reinforcement panel must be limited

to a maximum of 50 mm. The spacing between

the fasteners must not exceed 150 mm and the

glued area per screw is limited to 15,000 mm².

The only feasible fasteners in this case are

partially threaded screws with approval / ETA.

The length of the smooth shank must at least

correspond to the thickness of the reinforcement

panel. The adhesive used must, according to

the relevant approval, be suitable for use with

load­bearing screw gluing.

To avoid additional stresses in the glue joint, the

moisture content content in the members to be

connected must not differ by more than 4 %. For

rehabilitations, it is thus advisable, e. g. to place

the reinforcement boards in the building for some

time before the actual gluing.

9.3 Applications

9.3.1 Connections loaded at an angle to the

grain

For tensile loads acting perpendicular to the

member axis, there is a risk of tensile failure

perpendicular to grain, when forces are intro­

duced close to the loaded edge. The governing

fastener is the fastener furthest away from the

loaded edge.

In the design of reinforcement perpendicular to

the grain a cracked cross­section is assumed. In

other words, the reinforcing elements must be

capable of transferring the complete tensile loads

perpendicular to the grain.

Example 18: Connection loaded perpendicu-

lar to the grain using Beam

BauBuche GL75

Loads:

FEd = 45 kN, kmod = 0.7, service class 2

Dimensions:

Beam BauBuche GL75 140/240 mm

Figure 25: Geometry of screw gluing

Glued joint t

≥ 0

≥ 40 mmd ≥ 4 mm

≥ t

Table 49: Conditions for screw gluing in accordance

with DIN 1052­10, Chap. 6.2

Thickness of reinforcement panel

tmax = 50 mm (wood­based panel)

Fastener

Self­drilling partially threaded screw according

to approval / ETA with:

(1) ℓsmooth ≥ treinforcement panel

(2) Thread length in timber member including

screw tip

ℓef ≥ max(treinforcement panel; 40 mm)

(3) Nominal diameter d ≥ 4 mm

Arrangement

(1) Screw interval distances a1, a2 ≤ 150 mm

(2) Glued area per screw a1 · a2 ≤ 15,000 mm2

(3) Uniform grid when a1 = a2 = 120 mm

Member

(1) Moisture content u ≤ 15 %

(2) Moisture difference Δu ≤ 4 %

(3) Surface planed or sanded

Adhesive

Permissible for screw gluing

Company

Accredited for gluing in accordance with

DIN 1052­10

50

Connection:

max. distance between

fastener and loaded edge he = 150 mm

Width of the fastener group ar = 50 mm

Number of the fastener rows n = 3

Angle between load and

grain direction = 90°

Fastener diameter d = 10 mm

The load­carrying capacity of the non­reinforced

connection is

18 · h2e

F90,Rd = ks · kr · 6.5 +―――― · (tef · h)0.8 · ft,90,d

h2

18 · 1502

F90,Rd = 1.0 · 1.83 · 6.5 +――――― · (120 · 240)0.8 · 0.32

2402

= 29,300 N (NA. 104)

where 1.4 · arks = max 1 ; 0.7 +―――――

h

1.4 · 50 = max 1 ; 0.7 +――――― = 1.0 (NA. 105)

240

n 3

kr = ――――――=――――――――――――= 1.83 n h1 90 90 ∑ ――

2

1 + ――― 2

+ ――― 2

(NA. 106) i=1 hi 190 140

tef = min {b; 2 · tpen; 24 · d}

= min {140; 2 · 60; 24 · 10} = 120 mm

Since F90,Rd < FEd the connection must be rein­

forced. The reinforcement consists of two fully

threaded screws, which must be designed for the

following tensile force:

he 2 he

3

Ft,90,d = 1 ­ 3 · ―― + 2 · ―― · FEd

h h

150 2 150

3

= 1 ­ 3 · ――― + 2 · ――― · 45 kN (NA.69)

240 240

= 14.2 kN

9.3.2 Notched supports

Perpendicular to grain tensile stresses decline

very rapidly with increasing distance from the

notch. Accordingly, external reinforcing elements

must be installed up to the notch corner. Subject

to maintaining the minimum edge distances,

internal reinforcing elements should be arranged

as close as possible to the notch corner. For the

same reason, only the first fastener row in the

direction of the member axis may be taken into

account. To reduce the penetration depth and

hence the insertion resistance, constructive solu­

tions as shown in Figure 27 are possible.

Example 19: Reinforcement of a notch with

glued-on Board BauBuche

Loads: Vd = 10.3 kN, kmod = 0.9

Dimensions: GL28h, 100/250 mm

Height at the support hef = 145 mm

Distance to the notch x = 100 mm

Verification of the load­carrying capacity of the

notch

τd 1.07 N/mm2

η = ―――― = ―――――――――――――――― = 1.31 > 1.0

kv · fv,d 0.472 · 0.9 / 1.3 · 2.5 N/mm2

with

shear stress in the remaining cross­section

Figure 26: Connection loaded perpendicular to the grain

Figure 28: Notch with reinforcement

he

arh1 hi hn

b

tpen

tpen

h

Fv,Ed

FEd Fv,Ed/2 Fv,Ed /2

hef

h

ℓr

X

Lreq

Predrilling

diameter acc.

to screw

assessment

documents

(see Table 44)

Predrilling

diameter

≥ screw

diameter

L req

L req

Figure 27: Notch with reduced penetration depth

51

1.0 6.5kv = min ――――――――――――――――――――――――――――

250 0.58 · (1 ­ 0.58) + 0.8 100 1

­ 0.582

250 0.58

1.5 · Vd 1.5 · 10.3 · 103 N Nτd = ―――― = ―――――――――――― = 1.07 ――― (6.60)

b · hef 100 mm · 145 mm mm2

and the reduction coefficient kv

kv = 0.472 (6.62)

To reinforce the notch, Board BauBuche S

60 / 250 mm, t = 20 mm is applied on both sides

through screw gluing.

According to (NA.84), the following condition

applies for the width of the reinforcement panel

ℓr0.25 ≤ ――――― ≤ 0.5 (NA.84)

h ­ hef

This means that in this case, only a width of

ℓr ≤ 0.5 · (h ­ hef) = 0.5 · 105 = 52.5 mm

may be taken into account for the verification.

Determining the tensile force to be transferred by

the reinforcement Ft,90,d

Ft,90,d = 1.3 · Vd · 3 · (1 ­ )2 ­ 2 · (1 ­ )3 (NA.77)

= 1.3 · 10.3 · 3 · (1 ­ 0.58)2 ­ 2 · (1 ­ 0.58)3 = 5.1 kN

Verification of shear stresses in the glue line

τef,d 0.46 N/mm2

η = ――― = ――――――――― = 0.88 ≤ 1.0 (NA.80)

fk2,d 0.52 N/mm2

where

Ft,90,d 5.1 · 103 Nτef,d = ―――――――― = ――――――――― (NA.81)

2 · (h ­ hef) · ℓr 2 · 105 · 52.5

= 0.46 N/mm2

0.75 N/mm2

fk2,d = 0.9 · ―――――――― = 0.52 N/mm2

1.3

in accordance with Table NA.12

Verification of tensile stress in the reinforcement

panels

σt,dη = kk · ――――

ft,d

2.43 N/mm2

= 2.0 · ――――――――― = 0.12 ≤ 1.0 (NA.82)

41.5 N/mm2

where

Ft,90,d 5.1 · 103 Nσt,d = ――――― = ――――――― = 2.43 N/mm2 (NA.83)

2 · tr · ℓr 2 · 20 · 52.5

60 N/mm2

ft,d = 0.9 · ―――――――― = 41.5 N/mm2

1.3

The shear stress in the glue line is governing the

reinforcement design; the tensile strength of the

Board BauBuche is not attained.

9.3.3 Holes

Note: The design of holes in beams made of

BauBuche GL75 is currently excluded by the

declaration of performance.

Openings in beams with clear dimensions hd

exceeding 50 mm are to be considered as holes.

Perpendicular to grain tensile stresses at such

openings are caused by shear forces and bending

moments. When mainly shear forces are present,

cracks tend to appear at points 1 and 2 in Figure

29, while when bending moment prevails, the

cracks only appear at the upper edge (points 1

and 3). When designing the reinforcing elements,

all points at risk must be examined.

When designing reinforcements for openings, the

geometric conditions in accordance with Table 50

must be complied with.

Figure 29: Openings with transverse tensile cracks

hro + 0.15 hd

hru + 0.15 hd

3

3

2

2

1

1

hro

hro

hd

hd

Md

Md

ℓz

ℓz

a

a

ℓA

ℓA

ℓV

ℓV

Vd

Vd

Vd

Vd

h

h

hru

hru

52

Table 50: Requirements for reinforced openings

ℓz ≥ h, however at least 300 mm

ℓv ≥ h

ℓA ≥ h/2

hro(ru) ≥ 0.25 h

a ≤ h and a / hd ≤ 2.5

hd ≤ 0.3 h (for internal reinforcement)

hd ≤ 0.4 h (for external reinforcement)

Example 20: Reinforcement of a round

opening with glued-on

Board BauBuche

Loads: Md = 45 kNm, Vd = 30 kN

service class 1, kmod = 0.9

Opening: Glulam beam GL 24h

Beam width b = 140 mm

Beam height h = 240 mm

Remaining height hro = 92.5 mm

Remaining height hru = 92.5 mm

Diameter hd = 55 mm

Distance to end grain ℓV > 1,500 mm

Distance to support ℓA = 1,500 mm

hr = min{hro + 0.15 hd ; hru + 0.15 hd} = 101 mm

The design value of the tensile force perpendi­

cular to grain at the governing point is:

Ft,90,d = Ft,V,d + Ft,M,d = 3.58 + 3.57 = 7.15 kN

where (NA.66)

Vd · 0.7* · hd (0.7* · hd)2Ft,V,d = ――――――――― 3 ­ ――――――― = 3.58 kN

4 · h h2

* for round openings (NA.67)

Md MdFt,M,d = 0.008 · ―― = 0.008 · ――――――――― = 3.57 kN

hr hru/ro + 0.15 · hd

(NA.68)

For non­reinforced openings, the following con­

dition must be complied with:

Ft,90,dη = ―――――――――――――――――― ≤ 1.0 (NA.63)

0.5 · ℓt,90 · b · kt,90 · ft,90,d

(3.58 + 3.57) · 103 Nη = ――――――――――――――――――― = 2.10 > 1,0

0.5 · 139 · 140 · 1 · 0.35 N/mm2

where

ℓt,90 = 0.353 · hd + 0.5 · h = 139 mm (NA.65)

for round openings

kt,90 = min (1 ; (450/h)0,5) = min (1 ; (450/240) 0.5) = 1.0

To transfer the perpendicular to grain tensile

stresses, panels 240 / 210 mm, t = 20 mm made of

Board BauBuche S are glued on both sides.

Verification of the shear stress in the glue line

(governing!)

τef,d 0.50 N/mm2

η = ――― = ――――――――― = 0.96 ≤ 1.0 (NA.87)

fk2,d 0.52 N/mm2

where

Ft,90,d 7.15 · 103 Nτef,d = ―――――― = ―――――――――――――― (NA.88)

2 · ar · had 2 · 83.4 mm · 85.8 mm

= 0.50 N/mm2

0.75 N/mm2

fk2,d = 0.9 · ―――――――――― = 0.52 N/mm2

1.3

had = h1 + 0.15 · hd = 77.5 + 0.15 · 55 = 85.8 mm

ar ≤ 0.6 · ℓt,90 = 83.4 mm (NA.91)

9.3.4 Apex area of beams with variable cross-

sections

For economic and aesthetic reasons, long glulam

beams are normally designed with a variable

beam height and with or without curvature. The

kink in the beam axis in the apex generates per­

pendicular to grain stresses. The risk of cracks due

to tensile stresses perpendicular to the grain is

increased under unfavourable climatic conditions.

Example 21: Pitched cambered beam with

tensile cracks

Repair of a crack in the apex area of a pitched

cambered beam

Loads: Md = 340 kNm, kmod = 0.9

Dimensions:

Material GL 28c, b = 200 mm

Height in the apex hap = 1,462 mm

Roof angle δ = 15°

Angle of lower edge β = 9°

Length of apex area c = 2,200 mm

Figure 30: Reinforcement of a round opening

h1

ar ara tr trb

hro

hd hd h

h1 hru

53

For the reinforcement of the apex area glued­on

panels made of Board BauBuche Q are used on

both sides.

Verification of perpendicular to grain tensile

stresses in the apex cross­section

σt,90,dη = ――――――――――― (6.50)

kdis · kvol · ft,90,d

0.29 N/mm2

= ――――――――――――――――――― = 1.26 > 1

1.7 · 0.39 · 0.9 / 1.3 · 0.5 N/mm2

where

6 · Map,dσt,90,d = kp · ―――――――――

b · h2

ap

6 · 340 · 106

= 0.06 · ―――――――― = 0.29 N/mm2 (6.54)

200 · 1,4622

kdis = 1.7 (6.52)

0.01 0.2 0.01 0.2

kvol ≈ ――― ≈ ――― = 0.39 (6.51)

V 1.10

kp = 0.06 where

k5 = 0.054, k6 = 0.035, k7 = 0.276 (6.56)–(6.59)

Verification of reinforcement

To take into consideration the decrease of perpen­

dicular to grain tensile stresses in the longitudinal

direction of the beam, the tensile force in both

the external quarters of the affected area may be

reduced by a third.

The tensile force per reinforcement element is

σt,90,d · b · a1Ft,90,d = ―――――――――

n

0.29 · 200 · 1,205 · 10­3

= ――――――――――――――― = 35.0 kN (NA.101)

2

and in the external quarters

2 σt,90,d · b · a1Ft,90,d = ―― · ――――――――

3 n

2 = ―― · 35.0 kN = 23.3 kN (NA.102)

3

Verification of glue line in the governing internal

quarters

τef,d 0.09 N/mm2

η = ――― = ――――――――― = 0.09 ≤ 1 (NA.97)

fk3,d 1.04 N/mm2

where

2 · Ft,90,dτef,d = ―――――――

ℓr · ℓad

2 · 35.0 · 103 N = ――――――――――――― = 0.09 N/mm2 (NA.98)

1,153 mm · 679 mm

1.5 N/mm2

fk3,d = 0.9 · ――――――― = 1.04 N/mm2 (Tab. NA.12)

1.3

Verification of tensile stress in the glued­on rein­

forcement panels (Board BauBuche Q, t = 20 mm)

σt,d 1.52 N/mm2

η = ――― = ――――――――― = 0.05 ≤ 1 (NA.99)

ft,d 31.8 N/mm2

where

Ft,90,dσt,d = ―――――

tr · ℓr

35.0 · 103 N = ――――――――――――― = 1.52 N/mm2 (NA.100)

20 mm · 1,153 mm

46 N/mm2

ft,d = 0.9 · ――――――― = 31.8 N/mm2

1.3

9.4 Cross­sectional reinforcements

When additional loads are imposed, e. g. due to

changes in use, adding extra storeys to existing

constructions, or due to damage, there may be a

need to reinforce individual members.

9.4.1 Member reinforcement without con nection

The simplest type of reinforcement involves add­

ing additional members. The loading qi, to which

the individual cross­sections are exposed, can be

determined for beams via the ratio η of their

bending stiffnesses.

q1 = η · q ; q2 = (1 ­ η) · q

1where η = ――――――

(El)2

――― + 1 (EI)1

Figure 31: Pitched cambered beam

V

hap

ha

hrhx

x c

L

r trin

a

δ

β

54

The prerequisite is uniform loading, both of the

original member as well as the reinforcement,

e. g. by battens or planks. In addition, all load­

bearing members must be supported.

It is important to note that subsequently installed

members cannot accommodate pre­existing

loads. This underlines the need to relieve the load

on existing members as far as possible.

Example 22: Strengthening of timber beams

The intention is to strengthen existing timber

beams cross­section by adding a Board BauBuche.

Loads: qd = 10.0 kN/m, Md = 31.3 kNm

service class 1, kmod = 0.9

Existing members: C 24, 140/240 mm,

Reinforcement: Board BauBuche S,

40/240 mm

1η = ―――――――――――――――― = 0.70

16,800 · 4.61 · 107

―――――――――――― + 1 11,000 · 1.61 · 108

The loading on the existing beams is reduced to

0.7 · 10.0 = 7.0 kN/m. The utilisation factor for the

existing beams is thus 98 %. The reinforcement

with Board BauBuche S is used up to 47 %.

9.4.2 Reinforcement through mechanically

jointed members

9.4.2.1 Mechanically jointed members

By connecting additional members to existing

members by mechanical fasteners, it is possible

to create a composite cross­section, with a

load­carrying capacity far exceeding the sum of

the load­carrying capacities of the individual

cross­sections. Unlike members glued together in

accordance with Chapter 7, this does not, how­

ever, lead to an “ideal” composite cross­section,

since the flexible nature of the fasteners in the

joint line has a significant impact on the overall

load­carrying capacity. To connect individual

members nails, screws, bolts or dowels are used.

The shear forces acting in the joint lines cause

a deformation in the longitudinal direction of

the beam. The flexibility of the joint line can be

described by the slip modulus K and the fastener

spacing. By using inclined fully threaded screws,

more rigid joints can be established. For simplifi­

cation, the screws can be considered purely

axially loaded. The axial loading of the screws is

calculated by dividing the shear flow in the joint

line by the cosine of the insertion angle. Values

for the slip modulus of axially loaded fully thread­

ed screws can be taken from the respective

approvals / ETA.

Annex B of Eurocode 5 includes a design method

for mechanically jointed cross­sections in in

the form of the γ method. The applicability of the

γ­method is limited to the following:

– Individual components non­abutted over the

total beam length

– Cross­sections with constant geometry

– Uniformly distributed load in z direction

(sine or parabolic bending moment)

– Cross­sections made of two or three individual

components (a maximum of two flexible joint

lines)

Strictly speaking, the γ­method only applies for

pin­ended single­span beams. Multi­span beams,

however, can be calculated as single­span beams

of length ℓ = 0.8 · ℓ, whereby the shorter span

is used for ℓ. For cantilever beams, the doubled

length should be used.

The principle of the calculation method lies in

determining an effective bending stiffness (EI)ef,

taking into account the flexibility of the connec­

tion in the joint line. The flexibilities are expressed

by the γ­values. These can be assigned values

between 0 (no connection) and 1 (rigid connection;

glued). γ depends on the slip modulus K of the

mechanical fasteners and their spacing. Efficient

composite cross­sections are achieved by a staged

arrangement of the fasteners along the course of

A1,I1,E1

b1

b3

b2y

z

h1

0.5 h2

0.5 h1

a1

a3

0.5 h3

0.5 h2

h2a2

h3

A2,I2,E2

A3,I3,E3

Figure 32:

Geometry of

mechanically

jointed beams

0.5 b3

b2

y

z

0.5 h2

0.5 h1

a1

a3

0.5 h3

h1

h3

a2

0.5 h2

A1,I1,E1

A2,I2,E2

A3,I3,E3

0.5 b1

55

the shear force. Here, the greatest spacing must

not exceed a value four times that of the smallest.

To facilitate the design, normally only the fastener

spacing in the external beam quarters and those

in the internal quarters differ from each other.

The parameters for the γ­method are calculated

as follows:

Effective bending stiffness (EI)ef

3Elef = ∑ (Ei · Ii + γi · Ei · Ai · a

2i ) (B.1)

i=1

where the coefficient γ can be determined as fol­

lows

1γ1 = ―――――――――――――― for i = 1 and i = 3 (B.5)

π2 · Ei · Ai · si

1 + ―――――――――― Ki · ℓ

2

γ2 = 1.0 (B.4)

The distance from the centre of gravity of the

cross­section i to the centre of gravity of the total

cross­section is

γ1 · E1 · A1 · (h1 + h2) ­ γ3 · E3 · A3 · (h2 + h3)a2 = ――――――――――――――――――――――――― (B.6)

2 · 3∑

i=1γi · Ei · Ai

h1 + h2 h2 + h3a1 = ―――――― ­ a2 a3 = ―――――― + a2

2 2

For cross­sections with webs over the total beam

height, h1 and h3 should have negative signs,

provided a2 is positive and smaller than or the

same as h2 / 2.

The following checks must be performed at the

ultimate limit state:

1. Stress at the centre of gravity in the res­

pective cross­sections

γi · ai · Ei · Mdσt(c),i,d = ―――――――――― (B.7)

(EI)ef

2. Maximum stress of the respective

cross­sections

0.5 · Ei · hi · Mdσm,i,d = ――――――――――― + σt(c),i,d (B.8)

(EI)ef

3. Shear stress

(γ3 · E3 · A3 · a3 + 0.5 · E2 · b2 · h2) · Vd

τ2,max,d = ――――――――――――――――――――― (B.9)

b2 · (EI)ef

where

h2 h = ―― + a2

2

4. Load­carrying capacity of the fasteners

γi · Ei · Ai · ai · si · VdFi,d = ―――――――――――― (B.10)

(EI)ef

Note: For fasteners with larger diameters in par­

ticular, the cross­sectional reductions caused

by fasteners in the tensile areas are taken into

account. For this purpose, the centre of gravity

stresses are multiplied by Ai / Ai,net , and the bend­

ing stresses in the extreme fibres by Ii / Ii,net .

If the conditions for the γ­method cannot be met,

the “shear analogy method” in accordance with

Kreuzinger can be used (not explained in more de­

tail at this point).

9.4.2.2 Mechanically jointed lateral reinforce-

ments

The version for member reinforcement presented

in Chapter 9.4.1 presumes direct load introduction

in the reinforcement members. In cases in which

the spatial constraints do not allow the new cross­

sections to reach the upper edge of the existing

member, additional cross­sections can still be

laterally attached with mechanical fasteners. The

calculation uses the γ­method shown in Chapter

9.4.2.1.

Apart from the shear forces from the composite

action, the fasteners must also transfer the load

portion of the superimposed load passed on

from the existing member to the reinforcement.

For stacked partial members, this portion can

be disregarded, since the load transferred by the

reinforcement member is accommodated by

direct contact due to the deflection of the mem­

ber on top.

For lateral reinforcements, the centre of gravity

of the reinforcement should be as close as possi­

ble to the centre of gravity of the existing member.

This keeps the loading of the fasteners resulting

from the composite effect on a low level.

Provided only one­sided reinforcements are pos­

sible, additional torsional stresses in the cross­

sections, particularly in timber cross­sections,

must be taken into consideration.

Example 23: Reinforcement of a beam with

laterally nailed-on BauBuche

sections

Caused by an extension, an existing purlin may be

subject to greater snow loads due to snow drift.

This additional load cannot be accommodated by

the existing cross­section. Since the thickness

of the roof should not be expanded, panels made

56

of Board BauBuche S are laterally connected with

nails as a reinforcement. The existing installations

do not allow reinforcement boards to be estab­

lished up to the upper edge of the purlins, which

means verification in accordance with Chapter

9.4.1 is not possible.

Loads: qd = 10.0 kN/m

Md = 31.3 kNm

Vd = 25 kN

service class 1, kmod = 0.9

Existing members: C 24, 140 x 240 mm, ℓ = 5.0 m

Reinforcement: Board BauBuche S,

2 x 30/200 mm

Connection: Nails 3.8 x 70 mm in two

rows, predrilled

To ensure economic use of the fasteners, the

spacing in the longitudinal direction of the purlin

is increased in both the internal quarters of the

purlin length.

Selected fastener spacing:

sexternal = 160 mm, sinternal = 400 mm

For an arrangement with two rows on both sides,

the calculated nail spacing results as:

sexternal = 40 mm, sinternal = 100 mm

To determine the effective stiffness, an effective

fastener distance is used:

seff = 0.75 · sexternal + 0.25 · sinternal = 55 mm

where sinternal ≤ 4 · sexternal

The load­carrying capacity of a laterally loaded

nail is Fv,Rd = 1.1 kN, the average slip modulus

Kmean is

200 240

30 30

33 2

140

Figure 33: Reinforcement measure for a beam

Kmean = 2/3 · ρ1.5m · d/23

= 2/3 · ( 420 · 800)1.5 · 3.8/23 = 1,540 N/mm

The calculation of the composite cross­section is

performed in accordance with the γ­method for

the cross­section shown type shown in Figure 32

on the right and reduced to two parts. The stiff­

ness values are determined without taking into

consideration the safety coefficients γM, since

only the ratio of the cross­sectional stiffness

values applies. The effect of creep deformations

is also disregarded, since solid timber and Bau­

Buche have the same deformation coefficient kdef.

The effective bending stiffness (EI)ef of the com­

posite cross­section is calculated from

1 1γ3=―――――――――― =――――――――――――――――――― = 0.26

π2 · Ei · Ai · si

π2 · 16,800 · 12,000 · 55 1+――――――― 1+―――――――――――――― Ki · ℓ

2 1,540 · 5,0002

(B.5)

γ2 = 1.0 (B.4)

and

γ1 · E1 · A1 · (h1 + h2) ­ γ3 · E3 · A3 · (h2 + h3)a2 = ―――――――――――――――――――――――――

2 · 3∑

i=1γi · Ei · Ai

­0.26 · 16,800 · 12,000 · (­200 + 240) = ――――――――――――――――――――――――――――――

2 · (1.0 · 11,000 · 33,600 + 0.26 · 16,800 · 12,000)

= ­2.5 mm (B.6)

h2 + h3 ­200 + 240a3 = ―――――― + a2 = ―――――――― ­ 2.5 = 17.5 mm

2 2

to

3Elef = ∑ (Ei · Ii + γi · Ei · Ai · a

2i ) (B.1)

i=1

= 11,000 · 1.61 · 108 + 1.0 · 11,000 · 33,600 · 2.52

+ 16,800 · 4.0 · 107 + 0.26 · 16,800 · 12,000 · 17.52

= 2.46 · 1012 Nmm2

The small difference in height of the cross­sec­

tions cause only low tensile and compressive

stresses, meaning verifications of the centre of

gravity stresses can be disregarded.

Verification of bending stresses in the extreme

fibres

Md · E2 h2σm,2,d = ――――― · γ2 · a2 + ――

EIef 2

57

31.3 · 106 · 11,000 240 = ―――――――――――― · 1.0 · (­2.5) + ―――

2.46 · 1012 2

= 16.4 N/mm2 (B.8)

16.4η = ――― = 0.98 ≤ 1.0

16.6

(without reinforcement: η = 1.40)

where

24 N/mm2

fm,2,d = 0.9 · ――――――― = 16.6 N/mm2

1.3

Md · E3 h3σm,3,d = ――――― · γ3 · a3 + ――

EIef 2

31.3 · 106 · 16,800 200 = ―――――――――――― · 0.26 · 17.5 + ―――

2.46 · 1012 2

= 22.3 N/mm2 (B.8)

22.3η = ――― = 0.43 ≤ 1.0

51.9

where

75 N/mm2

fm,3,d = 0.9 · ――――――― = 51.9 N/mm2

1.3

Verification of maximum shear stress

(γ3 · E3 · A3 · a3 + 0.5 · E2 · b2 · h2) · Vdτ2,max,d = ――――――――――――――――――――――

b2 · (EI)ef

(0.26 · 16,800 · 12,000 · 17.5) · 25 · 103

= ――――――――――――――――――――――――

140 · 2.46 · 1012

(0.5 · 11,000 · 140 · 117.52) · 25 · 103

+ ――――――――――――――――――――――

140 · 2.46 · 1012

= 0.84 N/mm2 (B.9)

0.84η = ――― = 0.61 ≤ 1.0

1.38

where

4.0 N/mm2

fv,d = 0.9 · kcr · ―――――――― = 1.38 N/mm2

1.3

Fastener verification

The nail loads from the composite effect depend

on the shear force and the fastener spacing.

Vd (x) · γ3 · E3 · A3 · a3 · e (x)Fd = ――――――――――――――――― (B.10)

(EI)ef

The loads must be checked at the point of maxi­

mum shear force and at the beginning of the ex­

panded fastener spacing.

γ3 · E3 · A3 · a3 · sexternal · Vd (0)Fd(x = 0 m) = ――――――――――――――――――

(EI)ef

0.26 · 16,800 · 12,000 · 17.5 · 40 · 25 = ――――――――――――――――――――――――

2.46 · 1012

= 0.37 kN

γ3 · E3 · A3 · a3 · sinternal · Vd (1.25)Fd(x = 1.25 m) = ―――――――――――――――――――――

(EI)ef

0.26 · 16,800 · 12,000 · 17.5 · 100 · 12.5 = ――――――――――――――――――――――――

2.46 · 1012

= 0.47 kN

In addition, the fastener must transfer the load

portion, which is accommodated by the reinforce­

ment panels. This corresponds to the ratio of

bending stiffness of the reinforcements boards

(EI)3 to the overall stiffness (EI)ef.

(EI)3 16,800 · 4.0 · 107

――― =―――――――――――――― = 0.27(EI)ef 2.46 · 1012

The loading of the reinforcement boards is thus

0.27 x 10.0 kN/m = 2.70 kN/m.

The fastener in the internal quarters and perpen­

dicular to the member axis is subject to loading of

2.70 kN/m x 0.10 m = 0.27 kN.

The fastener subject to maximum loading with­

stands

Fd,res = 0.472 + 0.272 = 0.54 kN ≤ Fv,Rd = 1.1 kN

0.54η = ――― = 0.49 ≤ 1.0

1.1

where Fv,Rd = 1.1 kN

Example 24: Timber beams with screwed-on

panel strips made of BauBuche

Loads: qd = 3.2 kN/m, kmod = 0.8,

service class 1

Md = 14.4 kNm, Vd = 9.6 kN

Dimensions: (1) Board BauBuche S, hf = 60 mm

(2) C24 as a beam, 100/200 mm

Span ℓ = 6 m

Connection: fully threaded screws 6.0 x 200 mm,

Screw crosses inserted under 45°

Spacing: external quarter 120 mm,

internal quarter 300 mm

Fax,Rd = 13.6 kN per screw cross in

direction of the shear plane, acc. to

ETA­11/0190

(Note: Ignoring the distance of the centres of gravity)

58

Slip modulus of the fastener:

in axial direction per screw

Kax,ser,1 = 30 · 6 · ( 2 · 60) = 15,300 N/mm

Kax,ser,2 = 25 · 6 · (200 ­ 2 · 60) = 17,300 N/mm

1Kax,ser,ges =―――――――――――― = 8,100 N/mm

1 1

――――― +――――― 15,300 17,300

in joint line per screw cross

Kser = 2 · Kax,ser,ges · cos(45º)2 = 2 · 8,100 · 0.5

= 8,100 N/mm

Kmean = 2/3 · Kser = 2/3 · 8,100 = 5,400 N/mm

The effective fastener spacing is

seff = 0.75 · sexternal + 0.25 · sinternal

= 0.75 · 120 + 0.25 · 300 = 165 mm

Effective bending stiffness (EI)ef

3Elef = ∑ (Ei · Ii + γi · Ei · Ai · a

2i )

i=1

= 16,800 · 1.80 · 106 + 0.542 · 16,800 · 6,000 · 104.12

+ 11,000 · 6.67 · 107 + 1.0 · 11,000 · 20,000 · 25.92

= 1.36 · 1012 Nmm2 (B.1)

with the reduction coefficients γ

1γ1 = ――――――――――――――― π2 · E1 · A1 · s1 1 + ―――――――――― K1 · ℓ

2

1 = ――――――――――――――――――――― = 0.542 (B.5) π2 · 16,800 · 6,000 · 165 1 + ――――――――――――――― 5,400 · 6,0002

γ2 = 1,0

100 mm

60 mm1

2

200 mm

Figure 34: Timber beam

with Board BauBuche

The distances of the centres of gravity of the

cross­sectional parts from the centre of gravity of

the overall cross­section

γ1 · E1 · A1 · (h1+h2) ­ γ3 · E3 · A3 · (h2+h3)a2 = ―――――――――――――――――――――――― 3 2 · ∑ γi · Ei · Ai

i=1

0.542 · 16,800 · 6,000 · (60 + 200) = ――――――――――――――――――――――――――――

2 · (0.542 · 16,800 · 6,000 + 11,000 · 20,000)

= 25.9 mm (B.6)

60 + 200a1 = ――――――― ­ 25.9 = 104.1 mm

2

Verification of stresses in the centre of gravity

γ1 · a1 · E1 · Mdσc,1,d = ―――――――――

(El)ef

0.542 · 104.1 · 16,800 · 14.4 · 106

= ―――――――――――――――――――

1.36 · 1012

= 10.0 N/mm2 (B.7)

10.0η = ――― = 0.24 ≤ 1.0

42.5

where

1.2 · 57.5 N/mm2

fc,1,d = 0.8 · ――――――――――― = 42.5 N/mm2

1.3

γ2 · a2 · E2 · Mdσt,2,d = ――――――――――

(El)ef

1.0 · 25.9 · 11,000 · 14.4 · 106 = ―――――――――――――――――

1.36 · 1012

= 3.01 N/mm2 (B.7)

3.01η = ――― = 0.35 ≤ 1.0

8.62

where

14.0 N/mm2

ft,2,d = 0.8 · ―――――――― = 8.62 N/mm2

1.3

Verification of stresses in the extreme fibres

0.5 · E1 · h1 · Mdσm,1,d = ―――――――――― + σc,1,d

(El)ef

0.5 · 16,800 · 60 · 14.4 · 106 = ―――――――――――――――― + 10.0

1.36 · 1012

= 15.4 N/mm2 (B.8)

59

13.0η = ――― = 0.26 ≤ 1.0

49.2

where

80 N/mm2

fm,1,d = 0.8 · ――――――― = 49.2 N/mm2

1.3

0.5 · E2 · h2 · Mdσm,2,d = ―――――――――― + σt,2,d

(El)ef

0.5 · 11,000 · 200 · 14.4 · 106

= ――――――――――――――――― + 3.01

1.36 · 1012

= 14.7 N/mm2 (B.8)

14.7η = ――― = 0.99 ≤ 1.0

14.8

where

24 N/mm2

fm,2,d = 0.8 · ――――――― = 14.8 N/mm2

1.3

Verification of maximum shear stress

(γ 3 · E3 · A3 · a3 + 0.5 · E2 · b2 · h2) Vdτ2,max,d = ――――――――――――――――――――――

b2 ·(El)ef

(0.5 · 11,000 · 100 · 125.92) · 9.6 · 103

= ――――――――――――――――――――――

100 · 1.36 · 1012

= 0.62 N/mm2 (B.9)

where

h2 200h = ―― + a2 = ――― + 25.9 = 125.9 mm

2 2

0.62η = ――― = 0.50 ≤ 1.0

1.23

where

4.0 N/mm2

fv,d = 0.8 ·kcr · ――――――― = 1.23 N/mm2

1.3

Verification of fastener

γ1 · E1 · A1 · a1 · s1 · Vd (0)Fd (x = 0 m) = ――――――――――――――

(EI)ef · cos (45º)

0.542 · 16,800 · 6,000 · 104.1 · 120 · 9.6 = ―――――――――――――――――――――――――

1.36 · 1012 · cos (45º)

= 6.81 kN

9.5 Reinforced connection

Board BauBuche can be used to increase the

load­carrying capacity of connections with laterally

loaded fasteners. For this purpose, the Board

BauBuche is glued­on to the timber members in

the areas of the shear planes (see Figure 35).

Due to the higher embedding strengths of the

Board BauBuche in comparison to the timber

members to be connected, the load­carrying

capacity of the connection can be considerably

increased. Another very positive effect comes

in the reduced splitting risk, since the glued­on

reinforcement boards represent a form of

cross­reinforcement for the timber.

Werner (1995) sets out design equations for the

same. These are based on equations from Chapter

8 of Eurocode 5 (Johansen theory).

6.81η = ――― = 0.50 ≤ 1.0

13.6

0.542 · 16,800 · 6,000 · 104.1 · 300 · 4.8Fd (x = 1.5 m) = ――――――――――――――――――――――

1.36 · 1012 · cos (45º)

= 8.52 kN

8.52η = ――― = 0.63 ≤ 1.0

13.6

F

F

Figure 35: Reinforced

connection

(without reinforcement:

η = 1.46)

60

10.3 Strength values

The strength and stiffness design values for verifi­

cations in the load case fire are to be determined

in accordance with equations (2.1) and (2.2).

f20fd,fi = kmod,fi · ――― (2.1)

γM,fi

S20Sd,fi = kmod,fi · ――― (2.2)

γM,fi

Here, when using laminated veneer lumber and

the reduced cross­section method, both the

partial factor γM,fi as well as the mo dification

factor kmod,fi can be taken as 1.0. The 20 %­quan­

tile values are obtained from the 5 %­quantile

values multiplied by the correction factor kfi (for

laminated veneer lumber kfi = 1.1).

Accordingly, equations (2.1) and (2.2) can be

simplified to

fd,fi = 1.1 · fk

Sd,fi = 1.1 · S0,05

where

S0,05 = E0,05 bzw. G0,05

The design value of the load­carrying capacity of

a protected connection Rd,fi may be determined

from the characteristic load­carrying capacity at

normal temperature Rk as:

Rd,fi = kfi · Rk (2.3)

where

Note: For unprotected connections (not covered

here) the conversion factor η must also be used.

10.4 Actions

10.4.1 Design values of actions

The actions for the verifications in the load case fire

are to be determined in accordance with EN 1991­1­2.

Ed,fi = ∑ γGA,j · Gk,j + (ψ1,1 or ψ2,1) · Qk,1 + ∑ ψ2,i · Qk,i

(+ P + Ad)

Prestressing (P) is not covered in more depth at

this point. Accidental actions (Ad) need not be

taken into consideration for the load case fire.

Table 52: kfi ­values

1.15 Connection with side members made of

timber or wood­based panels

1.05 Connection with external steel plates

1.05 Axially loaded fastener

10 STRUCTURAL FIRE DESIGN

DIN EN 1991­1­2

DIN EN 1995­1­2

DIN EN 13501­1, 2

10.1 General

With regard to timber constructions and fire,

unfortunately, given the fla mmable property of

wood, many people conclude that it is not suit­

able for use in buildings subject to fire resistance

requirements.

Although wood is combustible, the combustion

behaviour is slow and uniform above all. The com­

bustion is delayed by evaporation of water as well

as the formation of a protective charcoal layer.

This means the load­bearing behaviour of timber

members subject to fire actions can be effectively

predicted and thus calculated.

In most cases, the premature failure of the metal

fastener is thus the key factor governing the over­

all load­carrying capacity. Establishing suitable

construction details can thus significantly boost

the resistance duration.

10.2 Requirements

Whether individual members have to meet fire

protection requirements and the nature of such

requirements is to be taken by referencing state­

specific legislation.

Board BauBuche may be classified in material

class E ­ normally combustible in accordance with

DIN EN 13501­1 and thus designed with the design

values for the combustion rate under Eurocode 5.

In Table 51, details of the fire resistance classes

in accordance with DIN EN 13501­2 are provided.

The figure indicates the time in minutes, for which

the load­carrying capacity of the member must

be maintained in the event of a fire.

The material class B2 in accordance with DIN

4102 corresponds to material class E in accor­

dance with DIN EN 13501­1.

The designation FXX of DIN 4102 for the fire

resistance classes corresponds to the designation

RXX of DIN EN 13501­2.

Table 51:

Fire resistance

classes

R30 Fire retardant

R60 Highly fire retardant

R90 Fire resistant

R120 Highly fire resistant

61

The combination coefficient used for the leading

variable load Qk,1 can be either ψ1,1 or ψ2,1.

Contrary to the Eurocode recommendation, how­

ever, in those cases in which wind or snow is the

leading variable load, ψ1,1 should be used.

10.4.2 Simplified determination of actions

For simplicity, the design value for actions Ed,fi

may also be derived from the action at normal

temperature at

Ed,fi = ηfi · Ed (2.8)

The reduction coefficient ηfi may either be deter­

mined from the diagram in Figure 36 or simplified

to 0.6 or for category E live loads to 0.7.

10.5 Design method

For design of timber members for the load case

fire, Eurocode 5 presents two simplified methods

– Reduced cross­section method

– Method with reduced strength and stiffness

values

The method with reduced properties is only

app licable to softwood and is thus not covered

in further detail at this point.

10.5.1 Reduced cross-section method

For this method, verifications are performed on

an effective cross­section. This is obtained by

deducting the charring depth as well as a transi­

tional layer between the combustion and the

unburnt wood, which is assumed to have no lon­

ger any strength or stiffness.

The strength and stiffness of the remaining (effec­

tive) cross­section are assumed to be unchanged

(see Chapter 10.3).

In addition, the following simplifications can be

made for verifications

– Compression perpendicular to grain can be

disregarded

– Shear can be disregarded for rectangular and

round cross­sections

– For braced members, either the functional

integrity of the bracing is to be verified or a

stability verification must be performed with

full buckling length.

0.6

0.7

reduction coefficient ηfi

load ratio Qk,1 / Gk

0.5

0.8

0.4

0.3

0.2

0.0 0.5 2.01.0 2.51.5 3.0

Figure 36: Reduction coefficient ηfi depending on the

load ratio Qk,1 to Gk (Figure 2.1)

Figure 37: Definition of

remaining and effective

cross­section in a fire

1 original cross­section

2 remaining cross­section

3 effective cross­section

ψfi = 0.9

ψfi = 0.7

ψfi = 0.5

ψfi = 0.2

k0 · d0

dchar,n

1

23

dchar,0

def

10.6 Charring

10.6.1 Charring of unprotected members

To determine the remaining cross­section under

fire, a distinction is made between one­dimen­

sional charring dchar,0 and charring taking into

consideration corner roundings and cracks dchar,n.

The design of bar­shaped members must be

performed with the combustion depth dchar,n,

while for plate­like members, dchar,0 may be used.

dchar,0 = β0 · t (3.1)

dchar,n = βn · t (3.2)

The following values can be applied in this case

for BauBuche.

Table 53: Charring rates for BauBuche

Bar­shaped members: βn = 0.70 mm/min

beams, tension members, columns

Plate­like members: β0 = 0.65 mm/min

panels

The effective charring depth def for fire protection

verifications for a fire duration of more than

20 min is

def = dchar + k0 · d0 = dchar + 7 mm (4.1)

62

Here, the simplified determination with ηfi = 0.6

leads to uneconomical design. Determining via

Figure 36, conversely, allows a more accurate cal­

culation of the loads.

10.6.2 Charring of protected members

Applying cladding panels can delay or even pre­

vent the start of the charring. The charring of

only initially protected members is calculated in

accordance with

0 ; t ≤ tf min {βn · ta ; 25} (t ­ tch) · ――――――――――― ; tf < t ≤ ta

dchar = (ta ­ tch)

βn · (t ­ ta) + min {βn · ta ; 25} ; t > ta

Here, for βn the values of the member to be pro­

tected can be used. tch describes the time up to

the point of failure of the fire protection cladding.

For fire protection claddings without gaps (smaller

than 2 mm) tch corresponds to the time of the

start of charring tf for the member to be protected.

The fire resistance duration tch of the cladding is

calculated for wood­based panels of thickness hp

and with a charring rate of

hptch = ――― (3.10)

β0

with β0 of the wood­based panel. The time limit ta is

2 · tf 25ta = min ―――― + tf (3.8)

2 · βn

with βn of the member to be protected.

Figure 38 shows the qualitative progression of the

charring of an initially protected member.

The rapid increase in charring (steep line) in

accordance with the failure of the fire protection

cladding is attributable to accelerated burning

of the preheated wood behind the cladding. From

a charring depth of 25 mm, the combustion pro­

gression is likely to be more normal, since by that

time, a sufficiently thick charcoal layer is present,

which delays the progression of the fire.

Figure 38 shows that while a thin protection

layer initially has a positive impact, this does not

last, with no further beneficial effect on the pro­

gression of the charring.

To prevent premature failure (collapsing) of fire

protection cladding, the fasteners must have a

penetration length into the non­charred member

of ℓA = min {10 mm ; 6 · d}.

R30 R60 R90 R120

dchar,0 19.5 39.0 58.5 78.0

dchar,n 21.0 42.0 63.0 84.0

def 28.0 49.0 70.0 91.0

β0 = 0.65 mm/min

for panels with d ≥ 20 mm (1st line);

βn = 0.7 mm/min

for bar­shaped members (2nd/3rd line)

β0 may be reduced for panel thicknesses smaller

than 20 mm and densities exceeding 450 kg/m3.

For Pollmeier Board BauBuche, no adaptation is

possible, since currently no boards below 20 mm

board thickness are produced.

Example 25: Bending stress verification for

a roof beam in the event of a fire

Beam BauBuche GL75, 160/240 mm, ℓ = 6.0 m,

e = 2.0 m, fire on three sides, R30

Loads: Dead weight gk = 1.50 kN/m2

Snow qk = 3.00 kN/m2

pd = 1.35 · 1.5 + 1.50 · 3.0 = 6.53 kN/m2

pd,fi = 1.0 · 1.5 + 0.2 · 3.0 = 2.10 kN/m2

The verification in the event of a fire is performed

based on a reduced cross­section. For a fire

duration of t = 30 min, the charring depth def is

def = 30 min · 0.7 mm / min + 7 mm = 28 mm

With the reduced section modulus, the verification is

18.9 · 106 Nmm ―――――――――――――――――――

σm,d, fi 104 mm · (212 mm)2 / 6

η = ―――― = ――――――――――――――― = 0.26 ≤ 1,0 fd,fi 94.1 N/mm2

where

fd,fi = kfi · kh,m · fm,k = 1.1 · 1.14 · 75 N/mm2 = 94.1 N/mm2

2 m · 2.10 kN/m2 · (6 m)2Md,fi = ―――――――――――――――― = 18.9 kNm

8

bef = 160 mm ­ 2 · 28 mm = 104 mm

hef = 240 mm ­ 28 mm = 212 mm

Alternatively, pd,fi can also be determined in sim­

plified form with the reduction coefficient ηfi = 0.6

from the design value of the governing load com­

bination at normal temperature

pd,fi = 0.6 · 6.53 kN/m2 = 3.92 kN/m2

or from Figure 36 depending on the load ratio qk / gk

pd,fi = 0.33 · 6.53 kN/m2 = 2.15 kN/m2

Table 54:

Charring depths

in mm of panels

and beams

made of

BauBuche

63

Example 26: Charring of a member with cladding

The following example shows the charring depths

for fire protection cladding made of BauBuche and

fire resistant plasterboards. To facilitate comparison,

the combustion of the unprotected cross­ section

is specified.

Figure 38: Qualita tive progression of the charring of an

initially protected member

Charring depth d

tf

d = 25 mm

ta tatf Time t

thin protection layer unprotected

effective protection layer

Board BauBuche

β0 = 0.65 mm/min

hp = 20 mm 25ta = min 2 · 30.8 min ; ――――――― + 30.8 min

2 · 0.7 mm

―――― min

= min {61.5 ; 48.6} = 48.6 min

tch = hp / β0 = 20 mm / 0.65 mm/min = 30.8 min

Plasterboard

hp = 12.5 mm 25ta = min 2 · 21 min ; ――――――― + 21 min

2 · 0.7 mm

―――― min

= min {42 ; 38.9} = 38.9 min

tch = 2.8 · hp ­ 14 = 2.8 · 12.5 ­ 14 = 21 min

Protected member

βn = 0.7 mm/min

For a fire duration of 30 min, the following char­

ring depths dchar,n(30) result

– BauBuche 0.0 mm

– Fire resistant plasterboard 12.6 mm

– Unprotected 21.0 mm

For a fire of 30­minute duration, the cross­section

can be completely protected by the Board BauBuche.

In Figure 39, the progression of charring is shown

for the various design versions.

Figure 39:

Progression

of charring for

various fire

protection

claddings

Time t in min

Charring depth d in mm

0 605040302010

0

50

40

10

20

30

Unprotected member

Plasterboard

BauBuche

10.7 Connections with timber side members

10.7.1 Unprotected connections

Unprotected connections are not covered here.

10.7.2 Protected connections

If fasteners are protected from the effects of fire

by cladding, it is important to ensure that the fire

resistance duration of the cladding tch exceeds

the required fire resistance duration of the con­

nection treq minus half the fire resistance duration

of the unprotected connection td,fi.

hptch = ―― ≥ treq ­ 0.5 · td,fi cf. (3.10); (6.2)

β0

From this results the required thickness hp of the

fire protective cladding made of BauBuche to

hp ≥ β0 · (treq ­ 0.5 · td,fi)

with a charring rate β0 = 0.65 mm/min for Board

BauBuche.

For laterally loaded fasteners in double­shear and

with timber side members, td,fi = 15 min, and for

connections with dowels, td,fi = 20 min.

Example 27: Fire protection cladding

for nail groups

The nail groups of the tensile connections of a

truss are designed for the fire resistance duration

R30. For this purpose, a fire protection cladding

made of Board BauBuche is selected to cover the

nail group.

The required panel thickness hp is revealed as

follows:

mmhp ≥ 0.65 ――― · (30 min ­ 0.5 · 15 min) = 14.6 mm

min

where the fire duration t = 30 min and the fire

resistance duration of the fastener td,fi = 15 min

To fasten the fire protection cladding in accordance

with DIN EN 1995­1­2, Gl. (3.16) it is important to

ensure that it is not at risk of falling off before the

start of charring tch of the member to be protected.

64

11 REFERENCES

Literature

Enders-Comberg, M., Blass, H.J. Treppenversatz –

Leistungsfähiger Kontaktanschluss für Druckstäbe.

Bauingenieur Band 89, 04/2014, Springer­VDI­Verlag,

Düsseldorf

Blass, H.J., Ehlbeck, J., Kreuzinger, H., Steck, G.

Erläuterungen zu DIN 1052:

Entwurf, Berechnung und Bemessung von Holz­

bauwerken. 2005, Bruderverlag, Munich

Kreuzinger, H. Verbundkonstruktionen.

Holzbau­ Kalender 2002, Bruderverlag, Karlsruhe

Werner, H. Empfehlungen für die Bemessung von

Verbindungen mit verstärkten Anschlussbereichen.

Bauen mit Holz 12/1995, Bruderverlag, Karlsruhe

Standards

DIN 1052-10 Design of timber structures – Part 10:

Additional provisions, May 2012

DIN 4102 Fire behaviour of building materials and

building components, May 1998

DIN EN 1990 Eurocode 0: Basis of structural design:

German version, December 2010

DIN EN 1990/NA National Annex Germany –

Eurocode 0: Basis of structural design, December 2010

DIN EN 1995-1-1/NA National Annex Germany –

Eurocode 5: Design of timber structures – Part 1­1:

General – Common rules and rules for buildings,

August 2013

DIN EN 1995-1-2 Eurocode 5: Design of timber

structures – Part 1­2: General – Structural fire design,

December 2010

DIN EN 1995-1-2/NA National Annex – Eurocode 5:

Design of timber structures – Part 1­2:

General – Structural fire design, December 2010

DIN EN 13501-1 Fire classification of construction

products and building elements – Part 1: Classification

using data from reaction to fire tests, January 2010

DIN EN 14374 Timber structures – Structural laminated

veneer lumber – Requirements, February 2005

ÖNORM B 1995-1-1 Eurocode 5: Design of timber struc­

tures – Part 1­1: General – Common rules and rules for

buildings, June 2015

ÖNORM B 1995-1-1/NA National Annex Austria – Euro­

code 5: Design of timber structures – Part 1­1: General –

Common rules and rules for buildings

SIA 2003 SIA 265 Timber structures. Swiss Society of

Engineers and Architects, Zurich

Approvals / ETA / declarations of performance

PM-005-2018 Declaration of performance – Laminated

veneer lumber made from beech. Laminated veneer

lumber according to EN 14374:2005­02 for non­load

bearing, load bearing and stiffening elements as of

27.07.2018. Pollmeier Furnierwerkstoffe GmbH, Creuzburg

PM-008-2018 Declaration of performance – BauBuche

GL75 beam. Glued laminated timber made of hardwood –

Structural laminated veneer lumber made of beech

according to ETA­14/0354 of 11.07.2018. Pollmeier

Furnierwerkstoffe GmbH, Creuzburg

ETA-14/0354 European Technical Assessment

ETA­14/0354 as of 11.07.2018. Glued laminated timber

made of hardwood – Structural laminated veneer

lumber made of beech. Austrian Institute of Construc­

tion Engineering, Vienna

ETA-11/0190 European Technical Assessment

ETA­11/0190 as of 23.07.2018. Self­tapping screws for

use in timber constructions. DIBt Deutsches Institut

für Bautechnik, Berlin

ETA-12/0197 European Technical Assessment

ETA­12/0197 as of 2019/02/28. Screws for use in

timber constructions. ETA­Danmark A/S, Nordhavn

Z-9.1-838 “German general construction technique

permit” as of 19.09.2018: Allgemeine Bauartgenehmi­

gung. Furnierschichtholz aus Buche zur Ausbildung

stabförmiger und flä­chiger Tragwerke – „Platte

BauBuche S“ und „Platte BauBuche Q“. Deutsches

Institut für Bautechnik, Berlin

Brochures

03 Building physics Brochure BauBuche – Building

physics as of October 2018. Pollmeier Furnierwerkstoffe

GmbH, Creuzburg

05 Fasteners Brochure BauBuche – Fasteners as of March

2019. Pollmeier Furnierwerkstoffe GmbH, Creuzburg

09 Wood preservation Brochure BauBuche – Wood

preservation and surface treatment as of February 2019.

Pollmeier Furnierwerkstoffe GmbH, Creuzburg

Gym, Islisberg

Architecture: Langenegger Architekten AG, Muri

Structural design: Makiol Wiederkehr AG,

Beinwil am See

Completion: Max Vogelsang AG, Wohlen

Photos: Yves Siegrist

66

12 APPLICATION EXAMPLES

Figure 41:

Connection de­

tails of trusses

Figure 40:

Trusses made of

Beam BauBuche

GL75

New construction of office and

production facilities – Trusses

The following application example is

based on the static calculation of the

office of merz kley partner ZT GmbH.

Trusses: Beam BauBuche GL75 (originally

planned and built in beam BauBuche GL70),

bottom chord 280/160, upper chord 280/180,

diagonals 280/160, posts 280/100 (edgewise

arrangement of panels)

Truss connections: Fixing system WS­T­7 of

SFS intec AG (in accordance with declaration

of performance No. 100144897)

service class 1, kmod = 0.9

280/160

280/

100

280/

100

280/160280/160

280/160 280/160

280/

300

280/180

36 mm after completion of building

58 mm after 10 years

91 mm after 10 years considerung snow load

Deformations displayed tenfold enlargedwithout camber of trusses

Joint

Joint Joint

+348

7400

1800

1000

25.000

Joint

TG Ø8x160 e=500 predrilled

2x3x6 WS-T-7 Ø7x133

no slot at the bottom side!

3 VG Ø8x300 predrilled

4 x FLA t=5 S235

4 x FLA t=5 S235

2x3x6 WS-T-7 Ø7x133 2x2x6 WS-T-7 Ø7x133

2x4x6 WS-T-7 Ø7x133

4 x FLA t=5 S235

2x2x6 WS-T-7 Ø7x133

2x2x6 WS-T-7 Ø7x133

2x3x6 WS-T-7 Ø7x133

3x5 CNa Ø6x80staggered by 6 mm parallel to grain direction

5 VG Ø8x200 100x200x16 S235

2x2x2 WS-T-7 Ø7x133

2 WS-T-7 Ø7x133

no slot at the bottom side!4 x FLA t=5 S235

no slot at the bottom side!

2 x FLA t=5 S235

2x1x6 WS-T-7 Ø7x113

2x1x6 WS-T-7 Ø7x113

2x4 WS-T-7 Ø7x133 60/160 C24Continuous joint

2x28 WS-T-7 Ø7x133per side

Dowel Ø10

Dowel Ø10 Dowel Ø10

12860 60

30

5

60

5

80

5

60

5

30

30 5x20

30

30 60 60 72 7260 30

305x20

30

9060 3060

90

30

30 60 60 30

30 220 30

20

60

45

45

30

20

4060

10

3025 4x40 35 30

1040

6050

150

10 80 10

480

10

10

10

10

305x20

30 305x

2030

10

10

10

10

160

1640

180

60

1015

0

30

5

60

5

80

5

60

5

30

1014

010

10

10

10

10

30 39 39 30

30 5x20

30

30 5x20

30

40

5x20

20

20

20 60 80 80 60 20

30 305x

2030

10

10

25

30 420 30

405x

20

20

20

540 540

100 7x60 20

Dowel

67

Production hall, elobau sensor technology, Probstzella, Thuringen

Architecture: F64 Architekten BDA

Structural design: merz kley partner ZT GmbH

Completion: Holzbau Amann GmbH

Photos: Michael Christian Peters

TG Ø8x160 e=500 predrilled

2x3x6 WS-T-7 Ø7x133

no slot at the bottom side!

3 VG Ø8x300 predrilled

4 x FLA t=5 S235

4 x FLA t=5 S235

2x3x6 WS-T-7 Ø7x133 2x2x6 WS-T-7 Ø7x133

2x4x6 WS-T-7 Ø7x133

4 x FLA t=5 S235

2x2x6 WS-T-7 Ø7x133

2x2x6 WS-T-7 Ø7x133

2x3x6 WS-T-7 Ø7x133

3x5 CNa Ø6x80staggered by 6 mm parallel to grain direction

5 VG Ø8x200 100x200x16 S235

2x2x2 WS-T-7 Ø7x133

2 WS-T-7 Ø7x133

no slot at the bottom side!4 x FLA t=5 S235

no slot at the bottom side!

2 x FLA t=5 S235

2x1x6 WS-T-7 Ø7x113

2x1x6 WS-T-7 Ø7x113

2x4 WS-T-7 Ø7x133 60/160 C24Continuous joint

2x28 WS-T-7 Ø7x133per side

Dowel Ø10

Dowel Ø10 Dowel Ø10

12860 60

30

5

60

5

80

5

60

5

30

30 5x20

30

30 60 60 72 7260 30

305x20

30

9060 3060

90

30

30 60 60 30

30 220 30

20

60

45

45

30

20

4060

10

3025 4x40 35 30

1040

6050

150

10 80 10

480

10

10

10

10

305x20

30 305x

2030

10

10

10

10

160

1640

180

60

1015

0

30

5

60

5

80

5

60

5

30

1014

010

10

10

10

10

30 39 39 30

30 5x20

30

30 5x20

30

40

5x20

20

20

20 60 80 80 60 20

30 305x

2030

10

10

25

30 420 30

405x

20

20

20

540 540

100 7x60 20

Dowel

68

Verification of bottom chord:

Nd = 857 kN (Tension), Md = 3.82 kNm

The tensile stress is

857 · 103 Nσt,0,d = = 25.4 N/mm2

(160 ­ 4 · 7) · (280 ­ 4 · 6) mm2

The design value of the tensile strength may be

increased by the coefficient kh,t, since the mem­

ber height is below 600 mm. In addition, the

coefficient kℓ has to be taken into consideration,

since the member length exceeds 3.0 m.

600 600kh,t =

0.10=

0.10= 1.08

h 280

3,000 3,000kℓ = min

s/2=

0.12/2= 0.92 = 0.92

ℓ 11,350

1.1

0.9ft,0,d = 1.08 · 0.92 · · 60 N/mm2 = 41.3 N/mm2

1.3

The bending stress is

3.82 · 106 N mm · 6σm,d ≈ = 5.14 N/mm2

(280 ­ 4 · 6) mm · (160 ­ 4 · 7 mm)2

The design value of the bending strength is

0.9fm,d = · 75 N/mm2 = 51.9 N/mm2

1.3

The verification of tension and bending in the

bottom chord is covered by

σt,0,d σm,d 25.4 5.14η = + = + = 0.71 ≤ 1.0 ft,0,d fm,d 41.3 51.9

Verification of posts: Nd = 68.7 kN (compression)

The compressive stress is

68.7 · 103 Nσc,0,d = = 2.45 N/mm2

280 mm · 100 mm

where

1.81 mλz = = 62.7

0.10 m / 12

From Table 14 kc,z can be derived at around 0.57.

The design value of the compressive strength

may be increased in service class 1 by the

factor 1.2.

0.9fc,0,d = 1.2 · 1.0 · · 49.5 N/mm2 = 41.1 N/mm2

1.3

The stability verification of the posts is covered by

σc,0,d 2.54 N/mm2

η = = = 0.10 ≤ 1 kc,z · fc,0,d 0.57 · 41.1 N/mm2

Verification of diagonals: The governing parame­

ters are Nd = 317 kN (compression), Md = 1.04 kNm

The compressive stress is

317 · 103 Nσc,0,d = = 7.08 N/mm2

280 mm · 160 mm

where

3.58 mλy = = 77.5

0.16 m / 12

From Table 14 kc,y can be derived at around 0.39.

The design value of the compressive strength in

service class 1 may be increased by the factor 1.2.

In addition, an increase may be achieved by the

coefficient kc,0.

kc,0 = min (0.0009 · h + 0.892 ; 1.18)

= min (0.0009 · 160 + 0.892 ; 1.18)

= min (1.04 ; 1.18) = 1.04

0.9fc,0,d = 1.2 · 1.04 · · 49.5 N/mm2 = 42.8 N/mm2

1.3

The bending stress is

1.04 · 106 N mm · 6σm,d = = 0.87 N/mm2

280 mm · (160 mm)2

The design value of the bending strength is

0.9fm,d = · 70 N/mm2 = 48.5 N/mm2

1.3

69

The stability verification of the diagonal is

covered by

σc,0,d σm,y,dη = + kc,z · fc,0,d fm,y,d

7.08 N/mm2 0.87 N/mm2

= + = 0.44 ≤ 1 0.39 · 42.8 N/mm2 48.5 N/mm2

Verification of the upper chord:

Nd = 825 kN (compression), Md = 13.5 kNm,

Vd = 33.1 kN

The compressive stress is

825 · 103 Nσc,0,d = = 16.4 N/mm2

280 mm · 180 mm

where

3.09 mλy = = 59.5

0.18 m / 12

From Table 14 kc,y can be derived at around 0.62.

The upper chord is braced by the roof panel.

The design value of the compressive strength

may be increased in service class 1 by the

factor 1.2. In addition, an increase may be

achieved by the coefficient kc,0.

kc,0 = min (0.0009 · h + 0.892 ; 1.18)

= min (0.0009 · 180 + 0.892 ; 1.18)

= min (1.05 ; 1.18) = 1.05

0.9fc,0,d = 1.2 · 1.05 · · 49.5 N/mm2 = 43.2 N/mm2

1.3

The bending stress is

13.5 · 106 N mm · 6σm,d = = 8.93 N/mm2

280 mm · (180 mm)2

The design value of the bending strength is

0.9fm,d = · 75 N/mm2 = 51.9 N/mm2

1.3

The stability verification in the upper chord is

covered by

σc,0,d σm,dη = + kc,y · fc,0,d fm,d

16.4 8.93 = + = 0.78 ≤ 1.0 0.62 · 43.2 51.9

The shear stress is

Vdτd = 1.5 · h · b · kcr

33.1 · 103 N = 1.5 (180 ­ 6 · 7) mm · (280 ­ 4 · 6) mm · 1.0

= 1.41 N/mm2

The design value of the shear strength is

0.9fv,d = · 8.0 N/mm2 = 5.54 N/mm2

1.3

The verification of shear in the upper chord is

covered by

1.41η = = 0.25 ≤ 1 5.54

Verification of truss connections (example given

for a connection loaded in tension in the bottom

chord): Nd = 652 kN (tension)

For the connections of the truss, according to the

static calculation of office merz kley partner ZT

GmbH, the fixing system WS­T­7 of SFS intec AG

was used. The design was conducted in accor­

dance with DIN EN 1995­1­1 with NA, paragraph 8

as a dowelled connection, taking into consider­

ation the details of the manufacturer as well as

the declaration of performance No. 100144897

of SFS intec AG. The design value of the load­

carrying capacity of a connection with multiple

shear planes and fasteners WS­T­7x133 mm is

provided as an example for the connection loaded

in tension in the bottom chord according to the

static calculation, Fv,Rd = 19.3 kN. The verification

of the connection loaded in tension (2 x 28 WS­T­

7x133 mm, 4 slotted­in steel plates) is met, taking

into consideration the effective number

of fasteners where

Ndη = Fv,Rd · nef

652 = = 0.81 ≤ 1.0 19.3 · (2 · 2 · 5.86 + 2 · 2 · 4.52)

The verification for the transfer of forces in the

steel plates is met with η ≤ 1.0.

70

71

Wooden skyscraper Suurstoffi 22, Risch

Posts and beams in BauBuche GL75,

Timber­concrete composite floors

Architecture: Burkard Meyer Architekten BSA

Structural design: MWV Bauingenieure AG

Completion: Erne AG Holzbau

Photos: Bernhard Strauss

72

73

Office building euregon AG, Augsburg

Frame construction: columns, beams from BauBuche GL75,

Structural floor construction from Board BauBuche Q, floor assembly from BauBuche Floor

Architecture: lattkearchitekten BDA

Structural design: bauart konstruktions GmbH

Completion: Gumpp & Maier GmbH

Photos: Eckhart Matthäus

74

Carpentry Anton Mohr, Andelsbuch

visible structural construction from Beam BauBuche GL75

Architecture: Andreas Mohr,

Structural design: merz kley partner ZT GmbH

Completion: Kaufmann Zimmerei

Photos: Christian Grass

75

Parking deck with timber­concrete composite slabs, columns and beams from BauBuche GL75,

Research project of TUM.Wood in cooperation of Professor Hermann Kaufmann,

Florian Nagler, Stefan Winter, Klaus Richter, Jan­Willem van de Kuilen

Imprint

Publisher:

Pollmeier Massivholz GmbH & Co.KG

Pferdsdorfer Weg 6

99831 Creuzburg, Germany

Phone +49 (0)36926 945­0, F ­100

info@pollmeier.com

www.pollmeier.com

Project management: Dipl.­Ing. Jan Hassan

Authors:

Univ.­Prof. Dr.­Ing. Hans Joachim Blass

Dipl.­Ing. Johannes Streib

Ingenieurbüro für

Baukonstruktionen

Blaß & Eberhart GmbH

Pforzheimer Straße 15b

76227 Karlsruhe, Germany

Photos:

Yves Siegrist,

Muri, Switzerland

Michael Christian Peters,

Amerang, Germany

Markus Bertschi,

Zürich, Switzerland

Eckhart Matthäus,

Wertingen, Germany

Christian Grass,

Dornbirn, Austria

Visualisations:

Hof 437, Thomas Knapp,

Alberschwende, Austria

Layout:

Atelier Andrea Gassner, Feldkirch, Austria

Reinhard Gassner, Marcel Bachmann

3rd revised edition 2019

Set in Univers Next

All rights reserved. Any utilisation out of

copyright is inadmissible without permission

of publisher and authors.

Download and order:

www.pollmeier.com