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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:
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