comparison of european and japanese seismic design of steel building structures

Engineering Structures 27 (2005) 827–840

www.elsevier.com/locate/engstruct

. Soil

stipulatedmandedive in EC8,rs becausetory

Comparison of European and Japanese seismic design ofsteel building structures

Edoardo M. Marino1, Masayoshi Nakashima∗, Khalid M. Mosalam2

Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan

Received 6 October 2004; received in revised form 7 January 2005; accepted 7 January 2005Available online 24 February 2005

Abstract

This paper compares EuroCode 8 (EC8) and the Japanese seismic design code (BCJ) for steel moment frames and braced framesclassification, magnitudeand shape of unreduced elastic response spectra, distribution of seismic shear along the height, memberductilityrequirements, and behavior factor are compared. It was found that the two codes are relatively similar except for the seismic forcefor the serviceability limit state. EC8 gives an approximately 2.5 times larger force for this limit state. Behavior factors that allow for systeductility are significantly different between the two codes; for moment frames BCJ is more conservative by about 50%. Strength demby EC8 and BCJ is evaluated for steel moment frames and chevron braced frames. Although the behavior factor is less conservatthe net strength required by EC8 is significantly greater than the corresponding BCJ strength for steel moment frames, and it occuof the significantly larger design force stipulated for serviceability inEC8. With regard to braced frames, BCJ leads to larger lateral sstrength except for chevron braced frames with slender braces.© 2005 Elsevier Ltd. All rights reserved.

Keywords: Seismic codes; Steel structures; Moment-resisting frames; Braced frames; Earthquake engineering

hisicic

cittlyngth

ea

.

ss

ss

sedhe

pted-ndu-enuc-enbleden-be-auseors,-

1. Introduction

EuroCode 8 (EC8) [1] will change its status from thepre-standard (ENV) to the European Standard (EN). T“new code”, which is to replace respective national seismstandards, introduces various innovative European seismdesign practices for steel buildings, such as the capadesign criteria and seismic force reduction factors explicicorrelated with expected ductility of the structure, amoothers. Many of such new concepts are already present innational seismic codes adopted recently in many Europ

∗ Corresponding author. Tel.: +81 774 38 4086; fax: +81 774 38 4334E-mail addresses: [email protected] (E.M. Marino),

[email protected] (M. Nakashima),[email protected] (K.M. Mosalam).

1 Tel.: +81 774 38 4085; fax: +81 774 38 4334. Permanent addreDepartment of Civil and Environmental Engineering, University of Catania,Italy.

2 Tel.: +81 774 38 4085; fax: +81 774 38 4334. Permanent addreDepartment of Civil and Environmental Engineering, University ofCalifornia, Berkeley, United States.

0141-0296/$ - see front matter © 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.engstruct.2005.01.004

y

en

:

:

countries (for example, DIN, 2002 [2], O.P.C.M., 2003 [3]).It is notable, however, that such codes are not widely uin real practice; rather, familiar provisions stipulated in told seismic codes (for example, DIN, 1981 [4], D.M.LL.PP.,1996 [5]) are most commonly used.

It is notable that Japan has a seismic design code adoin 1981 [6,7], called BCJ hereinafter, that explicitly considers two levels of seismic forces, one for serviceability athe other for safety. BCJ also accounts for force redistribtion after yielding due to redundancy, and trade-off betwestrength and ductility in accordance with the expected dtility of structures. The validity of such approaches has betested for twenty years of practical experiences. It is notathat many of the buildings designed by this code experiencea few significant earthquakes such as the 1995 HyogokNanbu (Kobe) earthquake. There are many similaritiestween the approaches adopted in EC8 and BCJ, but becof the physical distance, language barrier and other factthis Japanese seismic design code has not been fully recognized in other countries including those in Europe.

http://www.elsevier.com/locate/engstruct

828 E.M. Marino et al. / Engineering Structures 27 (2005) 827–840

reee

ethichtileanth

eearsry

hanehionlede

im

st,inge

resedttingthodadestfo

ioneenr ththefo

mia

. aC8ns

nce9) imiun

sticum isnte-d in

ing soilingg to

age

ase

ave

A

the

choil

he

ngandnd

intwo

-m,sis

n

This paper introduces an overview of BCJ and compamajor provisions stipulated in EC8 and BCJ. Here, stmoment-resisting frames and concentrically braced framare adopted as example structural types. Analyzingrespective provisions carefully, the paper examines whcode supplies design of stronger and/or more ducstructures. Such information is deemed useful for Europedesign practitioners and researchers to understandJapanese seismic design practices. It also gives themopportunities to calibrate and re-evaluate the respectivprovisions stipulated in EC8 in reference to the Japanescounterpart that has been tested for over twenty yeComparison on the surface, however, is often vemisleading. If one code stipulates a larger design force tthe other, it appears that a stronger structure is desigwith the former code. If this code gives a larger strengtreduction factor (behavior factor), however, the conclusmay no longer be valid. In the meantime, such detaicomparison and assessment of net differences between thseismic design code in the United States: UBC [8] andIBC [9], and BCJ had already been conducted by Nakashet al. [10] and Tada et al. [11].

The paper consists of the following parts. Fircomparison is made for the design seismic force includsoil classification and spectrum magnitude and shape. Thsecond part deals with strength and ductility of structuincluding the method of calculation, distribution of forcalong the height, behavior factor, requirements associatewith member ductility, and drift limits. The third parexamines the strength and ductility of steel moment-resisframes and concentrically braced frames designed bytwo codes, EC8 and BCJ. The Japanese seismic chad an overhaul in 2001, and new provisions are mavailable [12]. As compared to BCJ, the new code introducdifferent procedures for the estimation of seismic forces, buthe conventional BCJ procedures are also permitted. Asthe capacity oriented provisions such as strength calculatand ductility requirements, practically no change as bmade in the new code. For these reasons and also fosubstance of more than twenty years of implementation,conventional BCJ being in practice since 1981 is adoptedcomparison.

2. Seismic forces

Both European and Japanese codes define two seisforce levels. The reference seismic force (havingprobability of exceedance equal to 10% in 50 years, i.ereturn period equal to 475 years, according to both Eand BCJ) is representative of the strong ground motioThe other seismic force level (the probability of exceedaand return period are respectively 10% in 10 years andyears for EC8 and 50% in 30 years and 43 years for BCJrepresentative of moderate ground motions. In BCJ seisforce levels corresponding to moderate and strong gromotions are named Levels 1 and 2, respectively.

slse

e

.

nd

a

eee

rs

e

r

c

.

5scd

Ground motion is represented by means of an elapseudo-acceleration response spectrum. Such a spectrcorrelated with the foundation soil stratigraphy: differesoil types, ranging from hard to soft soils, and the corrsponding pseudo-acceleration elastic spectra are defineeach code.

In order to compare the seismic force levels stipulatedEuropean and Japanese codes, correspondence amontypes defined in EC8 and BCJ is established in the followsub-section. Subsequently, elastic spectra correspondinequivalent foundation soils are compared.

2.1. Soil types

EC8 classifies foundation soils by means of the avershear wave velocityVS,30. This parameter is evaluated withreference to the soil layers to the depth of 30 m from the bof the foundation as follows,

VS,30 = 30L∑

i=1

hiVi

(1)

whereL is the number of soil layers andhi andVi representrespectively the thickness (in meters) and the shear wpropagation velocity of thei -th soil layer. Five soil types,named A, B, C, D, and E, are specified. Soil typesand D represent hard soils(VS,30 > 800 m/s) and softsoils (VS,30 < 180 m/s), respectively. Soil types B and Cincorporate soils with intermediate characteristics andboundary between them isVS,30 = 360 m/s. Soil type Ecorresponds to a particular kind of soil stratigraphy in whia soft surface layer (type C or D) is placed over a hard s(type A).

BCJ defines three soil types, namely type I (hard), II(medium) and III (soft). The classification is made on tbasis of the fundamental period of the foundation soilTg

evaluated as follows,

Tg =

√√√√√32L∑

i=1

hi

(Hi−1+Hi

2

)V 2

i

(2)

where L represents the number of soil layers existibetween the base of the foundation and the rock soil,hi , Hi andVi represent respectively the thickness, depth ashear wave propagation velocity of thei -th soil layer.

Soil types defined by EC8 and BCJ are comparedFig. 1. Because different parameters are used by thecodes to classify the foundation soil (VS,30 in EC8 andTg

in BCJ), the comparison hasbeen carried out with reference to a unique soil layer, with thickness equal to 30placed over the rock soil. On the basis of this hypothethe average shear wave velocityVS,30, defined in EC8, andthe shear wave velocityVi in Eq. (2) are identical. There-fore, by substituting the limit values ofVS,30 given by EC8into Eq. (2), the soil classification stated in EC8 has beereformulated in terms of the soil fundamental periodTg.

E.M. Marino et al. / Engineering Structures 27 (2005) 827–840 829

Table 1Response spectra parametersclassified by soil type (EC8)

Soil type A B C D E Generic spectrum

S 1.00 1.20 1.15 1.35 1.40

TB (s) 0.15 0.15 0.20 0.20 0.15

TC (s) 0.40 0.50 0.60 0.80 0.50

TD (s) 2.00 2.00 2.00 2.00 2.00

-esBels

ra

forthe

um

ere islls,t

od

esticineda

rum

eII,orctra

t

oththeenra

in

tedrt

velm

hished

J,

Fig. 1. Soil types.

The hard soil types (soil types A in EC8 and I in BCJ) include substantially the same foundation soils in both codThe BCJ medium soil (type II) includes mainly soil typesand C. Finally, the BCJ soft soil (type III) includes soil typD in EC8. In summary, classifications of hard and soft soigiven by the two codes are relatively close to each other.

2.2. Response spectra

EC8 defines reference elastic spectraSe (in terms of thepseudo-acceleration) as a function of the building natuperiod,T , by means of the following expressions:

0 ≤ T ≤ TB Se = ag S

[1 + T

TB(2.5η − 1)

](3a)

TB < T ≤ TC Se = 2.5ag Sη (3b)

TC < T ≤ TD Se = 2.5agSηTC

T(3c)

TD < T ≤ 4.0 s Se = 2.5ag SηTC TD

T 2(3d)

ag = γI ag,R (3e)

where ag,R is the reference peak ground accelerationground type A (established in the national annexes onbasis of the seismic risk maps),γI is the importance factor,η is the damping correction factor (equal to 1 for 5% viscousdamping),S is the soil amplification factor, andTB , TC

andTD are characteristic periods of the response spectrdepending on the soil type.Table 1shows thevalues ofS,TB , TC and TD for different soil types. The value ofγI isassumed to equal 1.0 for ordinary buildings, while largvaluesare recommended when a large number of peoplexpected in the building (1.2 for schools, assembly haetc.) or when the functionality of the building is importanfor civil protection in the immediate post-earthquake peri(1.4 for hospitals, fire stations, etc.).

.

l

With reference to ordinary buildings,ag,R equal to 0.40g,and 5% viscous damping,Fig. 2(a) shows the EC8 referencelastic spectra corresponding to the several soil types. Elaspectra corresponding to moderate earthquakes are obtaby multiplying the ordinates of the reference spectra byreduction factorν. The recommended values ofν are 0.5for ordinary buildings and 0.4 for buildings with crowd andstrategic buildings.

BCJ stipulates the following expressions for elasticspectra Rt , with reference to a PGA equal to 0.40g(prescribed almost everywhere in Japan). The spectvalueRt is given as a fraction of acceleration of gravity.

0 ≤ T ≤ TJ Rt = 1 (4a)

TJ < T ≤ 2TJ Rt = 1 − 0.2

(T

TJ− 1

)2

(4b)

2TJ < T Rt = 1.6TJ

T(4c)

where theperiodTJ is determined according to the soil typand is equal to 0.4, 0.6 and 0.8 s for soil types I, II and Irespectively.Fig. 2(b) shows the BCJ Level 2 spectra. Fmoderate earthquakes, the ordinates of the elastic speRt are multiplied by 1C0 = 0.2. Note that BCJ does nostipulate an importance factor.

Fig. 3compares the EC8 and BCJ elastic spectra for bstrong and moderate earthquakes. For the purpose ofcomparison,ag,R that characterizes EC8 spectra has beset at 0.4g, identical to that stated in BCJ. The EC8 spectare plotted with reference to ordinary buildings (γI = 1.0andν = 0.5).

With reference to strong ground motions (Fig. 3(a)),EC8 spectra are slightly smaller than those providedBCJ except forT < 1.0 s, e.g. for medium soil, EC8spectrum is smaller by 10% to 30% than that stipulain BCJ. On the contrary, EC8 spectra are larger for shoperiod systems (20% larger for medium soil). With respectto moderate earthquakes (Fig. 3(b)), EC8 always specifieslarger elastic spectra, and differences in seismic force leare notable, e.g. for medium soil, EC8 spectrum is frotwo to three times larger than the BCJ counterpart. Tsignificant difference in the moderate ground motion is tmajor source that brings large differences in the strength anstiffness of steel moment frames designed by EC8 and BCas explicated later.


llewa

tdChdlfa

encIf

on

bey

ound

hichTheic

ngd a

d ofcthess.

o

hectoral

Fig. 2. Reference elastic spectra. (a) EC8, (b) BCJ.

3. Strength and ductility

Taking into account the ductility resources of structures,both EC8 and BCJ specify design seismic forces smathan those the structure should sustain if its responseelastic. At the same time, criteria and requirements aimingprovide the structure with necessary ductility are stipulateIn what follows, design procedures stated in EC8 and Bare summarized. Strength distributions along the heigseismic forcereduction factors for steel structures, anprovisions aiming to grant ductility required to individuastructural members (limits on width-to-thickness ratios ocross-sections and braces’ slenderness requirements)compared.

3.1. Seismic design forces according to EC8

According to EC8, the ultimate lateral strength of thstructure has to be large enough to sustain the refereseismic forces representative of strong ground motions.the structure meets the criteria for regularity in elevatiand has a fundamental period not larger than 4TC and2.0 s, the seismic response of the building mayevaluated by applying a set of horizontal forces to the stor

rs

o.Jt,

re

e

Fig. 3. Elastic response spectra for (a) strong and (b) moderate grmotions.

masses statically.TC is defined in the insert ofTable 1.Otherwise, the modal response spectrum analysis, wis not discussed in this paper, should be performed.seismic design base shearV1 due to the reference seismforces is given by,

V1 = Sd mλ (5)

wherem is the total mass of the building estimated by takiinto account the presence of the dead gravity load anfraction of the live gravity load,Sd is the ordinate of thedesign spectrum corresponding to the fundamental periothe buildingT1, andλ is a reduction factor of the seismiforces. The reduction factorλ takes into account the facthat in multi-story buildings the effective modal mass of tfundamental mode of vibration is smaller than the total maIn particular,λ = 0.85 if the building has more than twstories andT1 < 2TC , andλ = 1.0 otherwise. Thedesignspectrum Sd is obtained by reducing the ordinates of treference elastic spectrum by means of the behavior faq, which allows for the ductility expected for the structursystem. Details ofq will be discussed later.

The seismic forcesFi , which are distributed along theheight according to an inverted triangular distribution, are


e

ftheonatthdesh-ana

arorteer

iegn

htas

of

d

nt

e

a

l to

isonldar.

ceer

h

for

is

ifiedto,trstrgyby

tedunt

sey

eral

e

evaluated as follows,

Fi = V1zi mi

N∑j=1

z j m j

(6)

whereN is the number of stories, andmi andzi are thei -thfloor mass and height measured from the foundation levrespectively.

3.2. Seismic design forces according to BCJ

According to BCJ, the ultimate lateral strength oeach story of the structure has to be larger thandesign story shear corresponding to strong ground moti(Level 2 design). In addition, the stresses due to moderearthquakes (Level 1 design) should not exceedallowable stresses. It is notable that Japan has adoptesystem of design peer-review for the past three decadThe review is mandated for special structures like higrise structures (defined as those not shorter than 60 m)base-isolated structures. In the peer-review, seismic hazat the site is considered; site specific ground motionschosen; and nonlinear pushover and nonlinear time histanalyses are carried out to check whether or not the adopstructure satisfies the design criteria. Details of the pereview are presented by Pan et al. in [13]. The followingdiscussion excludes the design procedure with peer-revand is limited to the introduction of the static-based desiapproach used for common building structures.

Level 2 seismic forces are stipulated by a fixed heigdistribution of the minimum required story shear strengthfollows:

Vun,i = DS,i Fes,i 2V i (7a)

2V i = 2Ci

N∑j=1

w j (7b)

2Ci = Z Rt Ai 2C0. (7c)

In Eq. (7a), Vun,i is the required strength, DS,i is thestructural characteristic factor (conceptually, the inversethe behavior factorq), and Fes,i is the shapefactor setaccording to the distribution of the story stiffness aneccentricity of the plan. A specified subscript “i ” i ndicatesthat the quantity is referred to thei -th story. In Eqs. (7b) and(7c), 2Ci is the Level 2 story shear coefficient at thei -thstory, w j is the weight evaluated for the seismic designsituation at thej -th floor, Z is the seismic zone factor (equalto 1.0 for the high seismic hazard zone),Rt is the ordinateof the response spectrum corresponding to the fundameperiod of the building(T1), Ai is the height distributionfactor, and 2C0 is the standard shear coefficient for thLevel 2 seismic force equal to 1.0. The distribution factorAi ,which takes into account the higher mode effects, is givena function ofT1, such that:

Ai = 1 +(

1√αi

− αi

)2T1

1 + 3T1(8a)

l,

seea.

drdeyd-

w

al

s

αi =N∑

j=i

w j

W(8b)

whereW is the total weight of the building. The Level 1seismic force is stipulated by means of the followingformulas:

1V i = 1Ci

N∑j=1

w j (9a)

1Ci = Z Rt Ai 1C0 (9b)

where 1V i is the Level 1 story shear at thei -th story,1Ci isthe Level 1 story shear coefficient at the same story, and1C0is the shear coefficient for the Level 1 seismic force equa0.2, taken as one-fifth the Level 2 shear coefficient2C0.

3.3. Comparison of force distribution

For a ten-story building with uniform mass distribution,the distributions along the height of the shear strengthrequired by EC8 and BCJ have been evaluated. Comparis presented inFig. 4 for two values of the fundamentaperiod (T1 = 0.5 and2.0 s). The abscissa is the requirestory strength normalized with respect to the base sheFor the shorter period (T1 = 0.5 s), thedesign story sheardistributions for EC8 and BCJ are very close. The differenis at most 20%, which occurs at the top story. For the longperiod(T1 = 2.0 s), the difference is more pronounced, witthe largest difference (35%)observed at the top story. Infact, EC8 does not consider higher mode effects exceptstructures having long period (T1 larger than2.0 s) and/orvertical irregularity. In these cases the modal analysisrequired.

3.4. Behavior factor

In EC8, earthquake-resistant steel structures are classin three structural ductility classes with referencethe available ductility of their members: low (DCL)medium (DCM) and high (DCH). In addition, two differenapproaches may be used in design. According to the fiapproach, the expected structural behavior is low in enedissipation. The design internal forces are evaluatedmeans of elastic analysis, thestructure may belong to thelow ductility class (DCL), and aq-value greater than 1.5is not allowed. Aq-value equal to 1.5 takes into accounthe overstrength of the structure and, therefore, the expectbehavior is elastic. The second approach takes into accothe capability of the structure to resist the earthquakethrough the inelastic behavior of its members. In this cathe structure has to belong to the DCM or DCH ductilitclasses andq-values greater than 1.5 are allowed.

For high and medium ductility class structures thbehavior factor value is established on the basis of structutype and structural ductility class as summarized inTable 2.The value ofq is larger when structural types that ar


Table 2Behavior factorsq stated in EC8

Structural type Ductility classMedium High

Moment-resisting frames (MRFs) q = 4.0 q = 5αuα1

(6.5)

Diagonal braced frames (X-CBFs) q = 4.0 q = 4.0Chevron braced frames (V-CBFs) q = 2.0 q = 2.5Moment-resisting frames with concentric braces q = 4.0 q = 4αu

α1(4.8)

iortioflesr

ther,

first

thendorent-ces.

gostd

kup

s

ottoahe

tondriasand

oththeof

d
Fig. 4. Required story strength of ten-story buildings having uniform massdistribution. (a)T1 = 0.5 s, (b)T1 = 2.0 s.
considered more prone to exhibit a high dissipative behav(MRFs) and high ductility members are used. The raαu/α1 in Table 2 takes into account the redundancy othe structure and is specified according to the geometricaschemeof the system, e.g. 1.3 for moment-resisting framwith more than one story and more than one span, 1.2 fodual frames.

In BCJ steel structures are classified according toductility of their members. In particular, BCJ identifies foumoment-resisting frame classes, namely FA, FB, FC and FDand three classes of braces, namely BA, BB and BC. Theletter of the name indicates the structural type (F, moment-resisting frames; B, braces). The second letter indicatesability of the members to dissipate energy (A, B, C, aD correspond to members with high, good, fair and poductility, respectively). The ductility class depends on thwidth-to-thickness ratio of beams and columns in momeresisting frames and on the slenderness ratio for braDetails will be explicated inSection 3.6.

The BCJ structural characteristic factorDs is establishedas a function of member ductility for moment-resistinframes: the smallest value (0.25) corresponds to the mductile frame (FA), while larger values have to be usefor frames having smaller member ductility. Much morecomplex is the choice ofDs for braced frames. It is notablethat in Japan braces are always combined with bacframes having significant seismic strength and stiffness. Thisis very different from the European practice, in which braceare inserted in gravity supporting frames. Therefore,Ds -values stipulated in BCJ for such structures are related nonly to the ductility of the braces (brace class), but alsothe ductility of the backup frame (frame class), and toparameterβ, equal to the ratio of the shear sustained by tbraces to the total shear strength (Table 3).

In EC8, concentrically braced frames are classified intwo categories: diagonal braced frames (X-CBFs) achevron braced frames (V-CBFs). Different design criteand values ofq are stipulated for X- and V-CBFs. In framewith diagonal braces, compressive braces are ignored,the strength is estimated in reference to the yield strengthof braces in tension. In chevron braced frames, braces bin tension and compression are assumed to resist, andstrength is estimated in reference to the buckling strengthall the braces. Theq-values stipulated for chevron braceframes are equal to 2.5 and 2.0 for DCH and DCM ductility


Table 3Structural characteristic factorsDs stated in BCJ

Type of MRF Type of braceBA or BB BCβ = 0 β ≤ 0.3 0.3 < β ≤ 0.7 β > 0.7 β ≤ 0.3 0.3 < β ≤ 0.5 β > 0.5

FA 0.25 0.25 0.30 0.35 0.30 0.35 0.40FB 0.30 0.30 0.30 0.35 0.30 0.35 0.40FC 0.35 0.35 0.35 0.40 0.35 0.40 0.45FD 0.40 0.40 0.45 0.50 0.40 0.45 0.50

ce

Hse

ns

go

,e

eseratblfo

BC

ss

sforInMtha

orJ,

CJ

ethch

inhena

nsy

CJ

e

mely

classes, respectively. However, frames with diagonal bramay be designed with q equal to 4.0 for both DCH andDCM classes. Note that the distinction of X-CBFs in DCand DCM ductility classes is a mere formality becauthey are designed by means of the same criteria andq-value. The smaller values of q stated for V-CBFs maybe justified if their post-buckling behavior is analyzed. Ichevron braced frames, whenthe story shear force reachethe design value, buckling occurs in the brace sustainincompression. Because of reduction in the axial strengththe brace in compression during the post-buckling phasethe story shear strength of the frame may reduce below thdesign value.

While in EC8 emphasis is given to the structural schemthe braced frame classification reported in BCJ is baalso on the ductility of the braces: the smallest structucharacteristic factorDs is stipulated for frames with shorbraces (BA), which have the most dissipative and stainelastic behavior, and larger values should be usedframes with longer braces that belong to the BB andclasses.

3.5. Comparison of behavior factor

In Fig. 5(a), q-values stipulated in EC8 for MRFbelonging to the DCH, DCM and DCL ductility classeare compared with the inverse of theDs-factor stated inBCJ for FA, FB and FD frames, respectively. EC8 allowa larger reduction of the elastic seismic forces than BCJMRFs belonging to high and medium ductility classes.particular, behavior factors given in EC8 for DCH and DCmoment-resisting frames are about 60% and 20% larger1/Ds stated in BCJ for FA and FB frames.

Fig. 5(b) shows the comparison between behavior factq and 1/Ds stated for braced frames in EC8 and BCrespectively. Behavior factors 1/Ds reported inFig. 5(b) forBA, BB and BC braces are the smallest provided by Bfor each category. They have been obtained fromTable 3by coupling BA, BB and BC braces with the FD fram(the least dissipative according to BCJ) and supposingthe braces sustain almost the whole seismic force. Suchoice allows reproducing the usual bracing configurationEurope (backup frame supporting only vertical loads). Tcomparison is reported separately for frames with diagobraces and chevron braced frames.Fig. 5(b) showsthat the

s

f

,dl

er

n

s

ata

l

Fig. 5. Behavior factors comparison. (a) MRFs, (b) CBFs.

q-value established in EC8 for X-CBFs designed by meaof the capacity design criterion (DCH and DCM ductilitclasses) is 60% larger than 1/Ds given by BCJ for frameswith BA braces. For chevron braced frames EC8 and Bstipulate very comparable behavior factors.

3.6. Ductility of members

Local ductility ofmembers should be consistent with thexpected demand. In this regard, EuroCode 3 (EC3) [14]classifies the member cross-sections in four classes, na


ssss

FD-

d

an

th

MPEC

tio

thxia

th

efor

heisnd

imi

.

anyuntto

nd,ior

C8

1, 2, 3 and 4, with reference to the width-to-thickneratio of flanges and web. EC8 relates cross-sectional claallowed for structural members with theq-value, and theductility class adopted (Table 4). According to BCJ, thecross-sections of members in types FA, FB, FC andframes have to fulfill different limits for the width-tothickness ratio.

Table 4Cross-sectional requirement in EC8

Ductility class Behavior factor Cross-sectional classes allowe

DCL q ≥ 1.5 1, 2, 3 and 4

DCM1.5 < q ≤ 2.0 1, 2 and 32.0 < q ≤ 4.0 1 and 2

DCH q > 4.0 1

Width-to-thickness requirements provided by Europecodes (EC3 and EC8) and BCJ are compared inFig. 6 forwide flange cross-sections. The symbolsc, t f , d, and twrepresent the half width and the thickness of the flange,inner depth and the thickness of the web. The symbolε isdefined as follows,

ε =√

235

fy(10)

where the 235 represents a reference yield stress infor the S235 and SS400 steel grades according toand BCJ, respectively, andfy is the yield stress of theused steel (in MPa). In EC3, the width-to-thickness limit ofcolumn webs is given as a function of the stress distribuwithin the cross-section. InFig. 6(d),α, which represents theratio between the depth of the web part in tension andouter depth of the cross-section, varies from 0.0 (pure acompression) to 0.5 (pure flexure).

The two codes provide substantially similar limits wiregard to the width-to-thickness ratioof the flanges of bothbeams and columns (Fig. 6(a) and (b)). Limits regarding thweb are generally stricter in BCJ than in EC8 exceptcolumns of pure compression (Fig. 6(c) and (d)). Energydissipation of steel frames is provided primarily by tyielding of flanges; hence similar member ductilityexpected for the corresponding classification of EC8 aBCJ.

With regard to braces, EC8 establishes a maximum lfor the non-dimensional slendernessλ, defined as follows,

λ = λ

λy(11a)

λy = π

√E

fy(11b)

where E is the steel Young’s modulus andλ is theslenderness ratio. For both X-CBFs and V-CBFs,λ should

es

e

a3

n

el

t

Fig. 6. Width-to-thickness ratio requirements for wide flange cross-sections(a) Beam flange, (b) column flange, (c) beam web, (d) column web.

be not larger than 2.0. For X-CBFs,λ should be not smallerthan1.3.

The Japanese seismic code does not providelimitation on slenderness of braces. To take into accotheir different inelastic behavior, braces are classified inthree ductility classes (BA, BB and BC) according toλ. Infact, short braces do not buckle even in cyclic loading aconsequently, exhibit more stable and dissipative behavrelative to intermediate or long braces.Fig. 7 shows limitson non-dimensional slenderness of the braces given in EandBCJ.


Table 5Limits on inter-story drift in EC8 and BCJ

EC8 BCJNon-structural element Max∆l allowed (%) Non-structural element Max∆ l allowed (%)

Brittle 0.50 Commonly used 0.50Ductile 0.75

Drift tolerant 0.83No interferinga 1.00

a Non-structural elements fixed in a way soas not to interfere with structural deformation or without non-structural elements.

e

o

d.

aut

sn

ts

d

by

Jit

edte

gths

e

sual

ratetheJ

ines.

ilsre.

,r

Fig. 7. Slenderness requirements for braces.

4. Story drift requirement

According to EC8, the inter-story drift due to themoderate earthquakes can not be larger than the limit valugiven as percentages of the story height,∆l (Table 5). Suchlimits depend on the type of non-structural elements ftheir ability to accommodate the inter-story drifts withoutdamage.

Analogously, BCJ provides limits that have to be fulfilleby the inter-story drifts due to the Level 1 seismic forcesIn particular, two limit values of ∆l are given in BCJ(Table 5). The former and stricter limit is more commonlyapplied. The latter applies when non-structural elements ctolerate relatively large deformations of the structure withodamage.

When the maximum values∆l listed in Table 5 arecompared, it follows immediately that the two codeestablish analogous limits. Starting from this consideratiothe ratio of the EC8 to BCJ required stiffness(Kreq) isevaluated with reference to ordinary buildings (superscripE andJ refer to EC8 and BCJ, respectively):

K Ereq

K Jreq

= νλSe

g∆El

∆Jl

1C0Rt= ν

1C0

= 0.5

0.2= 2.50. (12)

Supposing∆El = ∆J

l and similar values ofλSe/g andRt

(seeFig. 3(a) where the EC8 spectrum should be multiplieby λ = 0.85 for short periods in reference toSection 3.1),the stiffness required by EC8 is 2.5 times that requiredBCJ. In conclusion, EC8 is significantly more stringent thanBCJ with respect to the stiffness requirement.

5. Lateral strength of moment-resisting frames

For ductile moment-resisting frames, both EC8 and BCallow large reductions in seismic forces in the ultimate lim

s,

r

n

,

Fig. 8. Lateral strength comparison between EC8 and BCJmoment-resisting frames.

state design. As a result, the design is generally controllby the inter-story drift requirement specified for moderaearthquakes. In this section, the actual story lateral strenof moment-resisting framesV E

R andV JR designed by means

of EC8 and BCJ are compared. The ratio betweenV ER and

V JR is given by the following equation (refer toAppendix A

for the derivation),

V ER

V JR

=[

νλSe

g 1C0Z Rt

∆Jl

∆El

(1 − γ ′ − 1

γ ′ s

)] 34

(13)

where s represents the contribution of columns to thtotal deformation. The parameterγ ′, which represents theamplification factor of the moment of inertia of the columninvolved by the capacity design criteria, is assumed to eq1.53 according toAppendix A. Eq. (13) accounts for theratio between seismic forces corresponding to the modeearthquakes stipulated in EC8 and BCJ, the ratio betweenmaximum values of inter-story drift angles allowed in BCand EC8 (assumed equal to unity according toSection 4),and the effect of the capacity design criterion stipulatedEC8 and represented in the term between the parenthes

The lateral strength ratio is reported inFig. 8 with refer-ence to the hard (type A and I) and soft (type D and III) soand as a function of the fundamental period of the structuPGA for a high seismicity zone is used (0.35g in EC8 and0.4g in BCJ). Because ordinary buildings are consideredν

is assumed 0.5.Z is fixed at 1.0. BCJ seismic shear facto


to

ys

er

bit

vioing

hedrynoat-e-

s ato

nhnedjaapbetiporl-

sdemthed iiou

-am

esexesthg tasid

mes.

tio

eld

is

J,nale

1C0 is taken to be 0.2. Beams and columns are supposedhave identical stiffness and therefores is taken 0.5.

Fig. 8 shows that, as a consequence of the significantllarger forces corresponding to the moderate earthquakeEC8, EC8 designed moment-resisting frames are strongmost cases. In particular, for short-period systems(T1 <

0.8 s) and for the soft soil, EC8 designed frames exhiabout 70% larger lateral strength.

As discussed inSection 3.6, width-to-thickness require-ments that control the member ductilities are similar be-tween EC8 and BCJ. Nevertheless, EC8 gives behafactors larger than BCJ by up to 60% for moment-resistframes (as noted inSection 3.5). Although various sourcesare plausible for this seemingly contradictory situation, twriters contend that the level of conservatism contemplatewith respect to the collapse margin is one of the primasources. The strength design using behavior factors isnecessarilyso explicit as to the maximum deformations ththe structure shall sustain. To compensate for the uncertainties, the trade-off between strength and ductility (dformation) inevitably includes conservatism. BCJ adoptstrength that takes into account force redistributions duemember yielding rather than the strength estimated based othe elastic analysis. The BCJ capacity design approacnot as rigorous as that adopted by EC8, although Japacolumns are commonly designed to be stronger than acent beams, say by a factor of 1.2, to ensure a beam collmechanism. These may result in smaller values for thehavior factors (meaning larger strength requirements) sulated in BCJ. The true answer to “which of the EC8BCJ behavior factors is more rational” will become avaiable only after full characterizations of structural collapsein earthquake conditions attached with inherent randomnesand uncertainties. This is indeed a focal subject in thevelopment of performance-based seismic design (for exaple [15]). It is also notable that the actual lateral strengis rather irrelevant to the strength requirements becausmore stringent serviceability requirements as discussethis section. This irrelevance may have lessened serinvestigations into this factor.

6. Lateral strength of braced frames

As reported inSection 3.4, EC8 adopts different strengthcriteria and differentq-values between frames with diagonal braces and chevron braced frames. By contrast, the srules apply in the design of both frame types according toBCJ. Two checks are required on the strength of the bracThe first is met when the compressive braces do notceed their buckling strength in the Level 1 seismic forcThe second is met when the ultimate lateral strength offrame is not smaller than the shear force correspondinthe Level 2 seismic forces. In this stage, braces in tensionconsidered yielded, while braces in compression are conered buckled. Strength criteria are stipulated in the associ-ated steel design standards (AIJ, 1973 and 1998 [16,17]).

inin

r

t

isse-

se--

--

ofns

e

.-.eore-

Fig. 9. Lateral strength comparison between EC8 and BCJ braced fra(a) X-CBFs, (b) V-CBFs.

With regard to frames with diagonal braces, the raof V E

R to V JR is given by the following equations (refer to

Appendix Bfor the derivation),

λ ≤ λ∗ V E

R

V JR

= Seλ

gq Z Rt Ds 2C0

[γM0(1 + χ Ju )] (14a)

λ > λ∗ V E

R

V JR

= Seλ

gq Z Rt 1C0

(2γM0χJb ) (14b)

where γM0 = 1.1 is the safetyfactor stated in EC3 forthe evaluation of yielding strength.χ J

b and χ Ju , which

are a function ofλ, are the buckling and post-bucklingstrength of the braces normalized with respect to the yistrength. These values are evaluated according to AIJ [17].The non-dimensional slendernessλ

∗, about 1.8 as shown

in Appendix B, separates ranges in which brace designcontrolled by Level 2(λ ≤ λ

∗) or Level 1(λ > λ

∗) seismic

force.The ratio of V E

R to V JR is reported inFig. 9(a) for the

medium soil (types B and II according to EC8 and BCrespectively), high seismicity zone and frames with diagobraces characterized byT1 < 0.6 s. Because Japanes


, iD

.

th

nto

e

te

ionhe

thily

es8

byy

ing,

es

heeag

gnd

ron

nsmicced

ongrekes,er.o

nd

g

fornt

llyseateoldil

gth8.heis

s isenthee

braces are always coupled with moment-resisting framesis supposed that the surrounding frame belongs to the Fcategory (least dissipative). Therefore,Ds is equal to 0.4or 0.5 whenλ is smaller or larger than 0.35, respectivelySince diagonal braces are allowed by EC8 only whenλ >

1.3 andλ < 2.0, only the solid line relationship is validin Fig. 9(a). This figure indicates that the lateral strengrequired by EC8 is about 50% smaller than that required byBCJ. Such a notable difference is attributed to the differevalues of the seismic reduction factors adopted by the twcodes, i.e.q = 4.0, whereas 1/Ds = 2.0, for the examinedstructures.

Comparison between chevron braced frames designby EC8 and BCJ is repeated inFig. 9(b). In this case, theratio of V E

R to V JR is given by(refer toAppendix Bfor the

derivation),

λ ≤ λ∗ V E

R

V JR

= Seλ

gq Z Rt Ds 2C0

γM1(1 + χ Ju )

2χ E(15a)

λ > λ∗ V E

R

V JR

= Seλ

gq Z Rt 1C0

γM1χJb

χ E. (15b)

Fig. 9(b) shows the ratio given by Eqs. (15a) and (15b)with reference to the chevron braced frame. Each paramein Eqs. (15a) and (15b) has the same value given in theprevious comparison except for theq-value, which is equalto 2.5. The normalized buckling strengthχ E given byEC3 depends by the shape of the braces’ cross-secthere wide flange shapes are considered. Elastic base sforcesSeλ/g and Rt are very similar forT1 < 0.6 s andmedium soils (seeFig. 3(a) where EC8 spectrum shouldbe multiplied by λ to equal 0.85 according toSection 3.1).Furthermore, q and 1/Ds stated respectively in EC8 andBCJ are equal (2.5 for the most dissipative systems). Inthe case of chevron braced frames, it is expected thatdifferences between EC8 and BCJ design come primarfrom the criteria used for the evaluation of the story shearstrength. The largest difference is observed for long brac(λ close to 2), where the actual lateral strength of the ECdesigned frame is almost 70% larger than that requiredBCJ. In fact, the actual ultimate story shear force given bEC8 is much larger than the design value (correspondto the buckling of braces in compression). As an examplethe shear force–displacement relationship for a single-storychevron braced frame with a pair of very slender brac(λ = 2.0) is shown inFig. 10. This figure shows that theactual lateral strength that corresponds to the yielding of tbrace in tension is about 2.5 times the design story shforce. It is notable that the actual strength of a pair of lonbraces becomes significantly larger than the design strengthwhen its design strength is estimated based on the bucklinstrength. Further discussion on this subject can be fouin [18].

t

d

r

:ar

e

r

Fig. 10. Shear force–displacement relationship for a single-story chevbraced frame(λ = 2.0).

7. Concluding remarks

This paper compares and examines the provisiostipulated in European (EC8) and Japanese (BCJ) seiscodes. Moment-resisting frames and concentrically braframes are considered, and the following main remarks canbe made.

1. The unreduced spectra corresponding to the strground motions stipulated in EC8 and BCJ acomparable. With reference to the moderate earthquadesign spectra provided by EC8 are significantly largFor systems havingT1 < 1.0 s, EC8 spectra may be up tthree times its BCJ counterpart.

2. Width-to-thickness requirements stipulated in EC8 aBCJ are similar. Nevertheless,EC8 gives behavior factorslarger than BCJ by up to 60% for moment-resistinframes.

3. Because of the large design seismic forces stipulatedthe serviceability limit state, the story drift requiremein EC8 appears significantlymore stringent than thatrequired in BCJ.

4. Seismic design of moment-resisting frames is generacontrolled by the serviceability requirements. Becauof the large seismic forces corresponding to moderground motions stipulated in EC8, European frames ha larger lateral story strength, by up to 70% for soft soand systems havingT1 < 0.8 s.

5. For frames with diagonal braces, the lateral story strenrequired by BCJ is about twice that required by ECBecause EC8 and BCJ provide equivalent criteria for testimation of the brace axial strength, the differenceattributed to the larger behavior factorq in EC8, which isabout twice that(1/Ds) in BCJ.

6. The lateral story strength of European chevron framesignificantly larger than its Japanese counterpart whslender braces are used. It is about 70% larger inconsidered case. This difference occurs primarily becaus


ore

nimllo

eng.

as

n

re

ees

ial

duth

s i

tia

rth

then

n:

geary

d

s 1

d

mrl

s.

the brace strength estimated by EC8 is significantly mconservative than that estimated by BCJ.

Acknowledgments

The first writer gratefully acknowledges the JapaSociety for the Promotion of Science (JSPS) for giving hgenerous financial support to study in Japan as a JSPS feand conduct the research reported in this paper.

Appendix A. Derivation of Eq. (13)

The actual lateral strengths of European and Japanmoment-resisting frames are evaluated. In the followisuperscripts,E and J refer to EC8 and BCJ, respectivelyWith reference to ordinary buildings(γI = 1.0) andexcluding very short-period structures, seismic design bshear force can be written as follows,

V E1 = SeλW

gq(A.1)

whereW is the weight of the building. Hereafter,Z Eb and

Z Ec represent the plastic modulus for beams and colum

cross-sections required by the above condition, whileI Eb and

I Ec are the corresponding moments of inertia. Furthermo

supposing that the inter-story drift∆E demanded byV E1

consists of two components, i.e.,∆Eb = (1− s)∆E , given by

the beams, and∆Ec = s∆E , given by the columns. To satisfy

the capacity design criteria,the design bending moment ofthe columns is obtained from,

Md,c = MG,c + 1.1γovΩ ME,c (A.2)

where MG,c and ME,c are the bending moments duto vertical loads (often neglected) and seismic forcrespectively; the coefficients 1.1 andγov = 1.25 takeintoaccount the hardening and overstrength of the materrespectively; andΩ is the minimum ratio between the actuaflexural strength and the bending moment of the beamsto the reference seismic forces, assumed to be 1.0 inderivation.

Therefore, the design bending moment of the columnsimplified asMd,c = 1.1γovME,c = γ ME,c = 1.375ME,c.Consequently, the plastic modulus and moment of inerof the columns should be increased toγ Z E

c and γ ′ I Ec ,

respectively. Because the moment of inertia and plasticmodulus of the members are proportional to the fouand third power of the member size, respectively,γ ′ =γ

43 = 1.53 can be reasonably assumed. This increase of

moment of inertia decreases the inter-story drift componassociated with the columns∆E

c .According to EC8, the inter-story drift during the

moderate earthquakes has to meet the following conditio

νq

(∆E

b + ∆Ec

γ ′

)≤ ∆E

l . (A.3)

w

se

e

s

,

,

l,

eis

s

et

Because of the great flexibility of moment-resistinframes, Eq. (A.3) is not generally satisfied. Then, thbeams and columns should be stiffened. The necessamplification factorαE is given by the ratio of the actualinter-story drift to the limit value stated in EC8 as follows,

αE =νq(∆E

b + ∆Ec

γ ′)

∆El

=νq(1 − γ ′−1

γ ′ s)

∆E

∆El

. (A.4)

Accordingly, the moments of inertia for the beams ancolumns areαE I E

b and αE γ ′ I Ec , respectively, if they are

stif fened proportionally.In BCJ, seismic base shear forces are given for Level

and 2 as,

1V J1 = 1C0Z Rt W (A.5a)

2V J1 = Z Ds Rt W. (A.5b)

Z Jb , Z J

c , I Jb , I J

c , and∆J in BCJ are analogous toZ Eb , Z E

c ,I Eb , I E

c , and∆E in EC8. The BCJ stiffness requirement canbe formulated as follows,

1C0

Ds∆J ≤ ∆J

l . (A.6)

If Eq. (A.6) is not satisfied,I Jb , I J

c may be proportionallyincreased by the following amplification factor,

α J = 1C0

Ds

∆J

∆Jl

. (A.7)

Accordingly, the moments of inertia for the beams ancolumns areα J I J

b andα J I Jc , respectively.

Supposing that moment-resisting frames fail in the beacollapse mechanism, the ratio between the actual shearesistancesV E

R (EC8) andV JR (BCJ) is approximately equa

to the ratio between the plastic modulus of the beams,

V ER

V JR

= Z Eb

Z Jb

=(

αE I Eb

α J I Jb

) 34

=[

νq Ds

1C0

∆E

∆J

∆Jl

∆El

(1 − γ ′ − 1

γ ′ s

)I Eb

I Jb

] 34

. (A.8)

Finally, considering that the inter-story drifts∆E (EC8)and ∆J (BCJ) are proportional to the design shear [Eq(A.1) and (A.5b) for EC8 and BCJ, respectively] and to theinverse of the moment of inertia of the cross-sections (1/I E

band 1/I J

b for EC8 and BCJ, respectively),∆E/∆J can bewritten as follows,

∆E

∆J= λSe

gq Z Ds Rt

I Jb

I Eb

(A.9)

and from Eqs. (A.8) and (A.9), Eq. (13) is obtained.


ainarld

ndth

e

e

ftha

dne

ing

mico

der

icfor

sisr

d[in

sisor

ns

Appendix B. Derivation of Eqs. (14) and (15)

In frames with diagonal braces, the braces that sustcompression are ignored, and the braces in tensionassumed to carry the axial forces corresponding to yiestrengthsN E

y . The required cross-sections of the first story

braces are obtained fromV E1 = V E

y , whereV E1 is obtained

from Eq. (A.1) andV Ey is expressed as follows,

V Ey = nN E

y cosθ = nAE

b fy

γM0cosθ (B.1)

where Ab is the area of the brace,γM0, equal to 1.1, isthe safety factor stated in EC3,n represents the number ofbrace pairs arranged in the story, andθ is the angle betweenthe brace and the beamlongitudinal axes. Accordingly, thecross-section area of one brace is estimated as,

AEb = γM0SeλW

gnq fy cosθ. (B.2)

In chevron braced frames, braces in both tension acompression carry seismic forces, with their axial strengassumed to equal the buckling strengthN E

b . The shearstrength is given by the following equation,

V Eb = 2nN E

b cosθ = 2nχ E AE

b fy

γM1cosθ (B.3)

where χ E is the ratio between the buckling and yieldstrength of the brace stipulated in EC3 as a function of thbrace slenderness, andγM1 = 1.1 is the safetyfactor statedin EC3. Accordingly, the required cross-section area of onbrace is estimated as,

AEb = γM1SeλW

2gnqχ E fy cosθ. (B.4)

As stated inSection 6, BCJ refers to brace bucklingstrength for Level 1 seismic forces, and a combination obrace yield and post-buckling strengths for Level 2. For boLevels 1 and 2 seismic forces, the required cross-sectionsobtained from1V J

1 = 1V Jb or 2V J

1 = 2V Ju where 1V J

1 and

2V J1 are obtained from Eqs. (A.5a) and (A.5b), respectively,

and 1V Jb and 2V J

u are expressed as follows,

1V Jb = 2nN J

b cosθ = 2nχ Jb AJ

b fy cosθ (B.5)

2V Ju = n(N J

y + N Ju ) cosθ = n(1 + χ J

u )AJb fy cosθ (B.6)

where χ Jb is the ratio between the buckling and yield

strength of the brace, andχ Ju is the ratio between the post-

buckling and yield strength of the brace, both specified inAIJ. Evaluation ofχ J

b and χ Ju is also reported by Tada

et al. [11]. Accordingly, the cross-sectional areas requireto sustain Levels 1 and 2 seismic shear forces are obtaias follows,

1AJb = Z Rt 1C0W

2nχ Jb fy cosθ

. (B.7)

e

re

d

Fig. 11. Ratio between Level 2 to Level 1 required area of braces accordto BCJ.

2AJb = Z Rt Ds 2C0W

n(1 + χ Ju ) fy cosθ

. (B.8)

Fig. 11 shows the ratio between2AJb and 1AJ

b . In thisplot, it is supposed that the braces resist the entire seisshear force(β > 0.7) and the surrounding frame belongs tthe FD category (Ds = 0.4 or 0.5 whenλ is smaller or largerthan 0.35, respectively). Level2 controlsthe design in a widerange of non-dimensional slenderness. Only for very slenbraces (λ ≥ λ

∗, with λ

∗ ≈ 1.8), BCJ Level 1 controls thedesign.

For frames with diagonal braces, Eqs. (14a) and (14b)are obtained from Eqs. (B.2), (B.7) and (B.8). For chevronbraced frames, Eqs. (15a) and (15b) areobtained from Eqs.(B.4), (B.7) and (B.8).

References

[1] CEN. EuroCode 8: Final draft ofEuroCode 8: Design of structuresfor earthquake resistance — Part 1: General rules, seismactions and rules for buildings. Bruxelles: European CommitteeStandardization; 2003.

[2] DIN. Buildings in German earthquake areas — Design loads, analyand structural design of buildings. Berlin: German Institute foStandardization; 2002 [in German].

[3] O.P.C.M. n. 3274, 20 / 03 / 2003. First principles concerning generalcriteria for the seismic classification of the national territory antechnical provisions for constructions in seismic area. Rome; 2003Italian].

[4] DIN. Buildings in German earthquake areas; design loads, analyand structural design; usual buildings. Berlin: German Institute fStandardization; 1981 [in German].

[5] D.M.LL.PP., 16 January 1996. Technical provisions for constructioin seismic area. Rome; 1996 [in Italian].

[6] BSL. Building standard law. 2000 [in Japanese].[7] BCJ. Structural provisions for building structures. 1997 edition—

Tokyo: Building Center of Japan; 1997 [in Japanese].[8] ICBO. Uniform building code. International conference of building

officials. Whittier; 1997.[9] ICC. International building code. International Code Council,

Whittier; 2003.


l

ofnd03

ding

nch

ln

5.

:

and

[10] Nakashima M, Roeder CW,Maruoka Y. Steel moment framesfor earthquakes in United States and Japan. Journal of StructuraEngineering, ASCE 2000;128(8):861–8.

[11] Tada M, Fukui T, Nakashima M, Roeder CW. Comparisonstrength capacity for steel building structures in the United States aJapan. Earthquake Engineering and Engineering Seismology 204(1):37–49.

[12] Midorikawa M, Okawa I, Iiba M, Teshigawara M. Performance-baseseismic design code for buildings in Japan. Earthquake Engineerand Engineering Seismology 2003;4(1):15–25.

[13] Pan P, Zamfirescu D, Nakashima M, Nakayasu N. Base-Isolatiodesign practice in Japan: Introduction to the post-Kobe approaJournal of Earthquake Engineering 2005;9(1):147–71.

;

.

[14] CEN. EuroCode 3: Design of steel structures — Part 1–1: Generarules and rules for buildings, ENV 1993–1–1. Bruxelles: EuropeaCommittee for Standardization; 1993 [in Italian].

[15] Performance-based seismic designconcepts and implementation. In:Proceedings of an international workshop. PEER Report 2004/1Berkeley: Pacific Earthquake Engineering Research Center; 2004.

[16] AIJ. Design standard for steelstructures. Tokyo: ArchitecturalInstitute of Japan; 1973 [in Japanese].

[17] AIJ. Guidelines for limit state design of steel structures. TokyoArchitectural Institute of Japan; 1998 [in Japanese].

[18] Marino EM, Nakashima M. A new tension-compression designapproach for chevron braced frames. Earthquake EngineeringStructural Dynamics [submitted for publication].

comparison of european and japanese seismic design of steel building structures

Documents