coDE 211997REPUBLIC OF IRAQ

IRAQI SEISMIG CODE REQUIREMENTSFOR BUILDINGS

BUILDING RESEARCH CENTRbGeneral Commission for Industrial Research and DevelopmentMinistry of Industry and Minerals

APROVED BY CENTRAL ORGANIZATION FORSTANDARDIZATION AND QUALITY CONTROL

IRAQI SEISMIC CODE REQUIREMENTS FOR BUILDINGScoDE 2 I 1997

CODE COMMITTEE

Dr. ADNAN FADHEL ZAIN ALAN Saddam University/College of Engineering(Chairman)

Dr. KA\YAN GAID ALANI National Centre of Engineering Consultancy

Dr. DAWOOD SHAKER ALBADRANI Iraqi N{eteorological and SeismologyOrganization

Dr. RAID I{ATTI ALKASS Building Research Centre

N{r. NAMIR NAJIB AMSO Union of Engineers

Dr. RIYADH JAWAD AZl7, Saddam University/College of Engineering

Dr. KHALID SAID DINNO Saddam University/College of Engineering

\Ir. BAHA GEORGE IKZER Building Research Centre

N{r. S^{A,D ABDUL WHAB Central Oreanization for Standardizationancl Qual i ty;Control

Dr. YASIN YAHYI YASIN Saddam University/College of Engineering

CONTENTS

Paee No.

CHAPTBR I - SCOPE AND PURPOSE . . . . . . . . . . . . T

CHAPTER 2 - PRINCIPLES OF BARTI{QUAI(E - RBSISTANT 2

1 DESIGN

2.l- Basic ConcePt2.2- Structural LaYout2.3- Structural SYstem2.4- DuctilitY2.5- Deformations2.6- Site Selection2.7'Seismic Joints2.8- Floor Structures

. C | I A P T E R 3 . B V A L U A T | O N o F S E I S M I C A C T I O N S . . . . . . . . . 5

3.I - General3.2- Evaluation of Seismic Design Forces for Equivalent Static Analysis

3.2.1- Seisrnic Hazatd and Zoning Coefficient - Z- 3 .2.2- ImPortance Factor - I

3'2.3- DYnamic Coefficient - S3.2.4- Stnrctural System Coefficient - K

3.2.5' Total Weight of Buildings and Structures - W

3.2.6- Influence of Soil and Fourrdation Conditions

3.3- Distribution of Seismic Forces

3.4- Method of Dvnamic Time History Analysis

CIIAPTBR 4 - VI,RIFICATION OF STRUCTURAL BEI-IAVIOIJR, ...... 18

STRESS CONDTTIONS AND DBFORMATIONS

cHAp'rBR s - coNsTRUC'rroN oF EARTI ' IQUAI(E RBSISTAN'r . . . . . . 2r

STRUCTURDS

I ,. 5.I-Reinforcecl Concrete Shuctures'

5.1.I-General, Dtrcti l i ty and Stlength Reqttirenrents

5.1.3-Frame SYstems5. 1 .4 -Wnl l SYstc t t t s

-i-

Pase No.5. 2-Prestressed Concrete Structures5.3-Steel Structures5 . 4-Prefabricated Structures5.5-Masonry Structures5.6-Foundations

5.6.1-General5.6.2-Soil Capacities5.6.3-Supersh ucture-Foundation Comection5.6.4-Foundation - Soil lnterface5.6.5-Special Requirements for I'�iles and Caissons

APPIINDIX A List of reports of Investigations for elaboration of prelirninary ...37

seisrnic design code of lraq

Al'PItNDliX l] Seisrnic Zoniug Map of lraq

RI'IIBITNCBS

. . . 3 9

. . . 40

-ii-

GHAPTIIR I 'SGOPE AND FUNPOSE

l.t- This code provides clesign and constructiort requirements for an earthquake

resistant buildings, towers, chimneys and similar structures'

The method specified do not cover nuclear power plants, large dams, and similal'

: installations which iequire special site and sffttctural investigations.

1.2-Thepurposeofanearthquakeresistantdesignis:- to prevent loss of life and human injury'- to ensure continuity of vital services'- to minimize damage to Property'

- l -

CI.IAP-TtrR 2 - PRINCIPLIIS OI ' I ' ,AI I ] ' I IQTJAI( I ' - ITITSIS' I 'AN'I ' DBSIGN

2.1- Basic Concept

'I '5c bnsio ogucopt of l"hc rcrluitcrnonts l lrovit lcd in tlr is coclc is l"lr itt" otlntPlctc

protectiol against total damage is not econornically feasible for all Wpes of buildings

ald sfiuctures. This concept is fulfilled by the following criteria:

a) T[e structure should withstancl, without atry structrrtal arrd norr-slructttl'al clamage,

the effects of slight seisrnic motion.

b) T6e str-ucture s|oulcl withstzurcl, with lirnitecl rron-stnrctural clarnagc and lirnitecl

non-lincar bchaviour of'struoturul rnclnbcrs, thc c{l 'cots o{'ttt<lclcratc scisttt ic ttroticltt

(design earthquake).

c) The sfructure should not collapse under sevel'or maximum expected earthquake.

2.2- Structural Layout

For bettel' earthquake resistance, it is necessary that buildirrgs and structurcs have

simple forms, in both plarr arrd elevatiotr, and of structural eletncttts which resisl

lorizontal seisrnic actions be arranged in such a way that torsional cffects arc

rninirnized. Non symrnetrical distribution of volulnes, lnasses attd stiffilesses in

buildirrgs should be avoided itt orcler to control torsional effects.

Gelerally, the design ald consh'uction of buildings and structures with irregular or

complicated layout shall be avoided due to the potential occurfellce of critical

additional sfiesses in the regions of discontinuities. When these requirements catrnot

be met, the str ucture shall be separated by seisrnic joints, each part having ir"n adequate

shape arrcl a proper clistribution of volutnes, masses and rigidities. Othcrwise propel'

coniideratiols of irregularities shoulcl be taken, suclt as by perfotnring appropriate

clynarnic analysis.

2.3- Structural System

The structural systern should be clearly defined so that rational analysis can be

applied. In computing earthquake response of a building, the influence of not only

sUucfural systems, but also non-sh'uctural elements (infill walls, partitions, windows.

etc.) should be considered as well.

-7-

2,4- Ductility

The structural system and its structural elements should have adequate sfrength ancl

ductility for the aiplied seismic actions. Structural elements which have sufficient

ductility are capable of absorbing energy. Special attention should be given to the

brittlenlss of structural elements such as shear failure, joint fracture, buckling, bond

failure and anchorage failure.

2.5- Deformations

The cleformations of the structure under seismic actions should be limited.

Generally, there are two kinds of defor:nations to be controlled: the inter-storey drift

(relative iateral displacement within a storey) and the absolute lateral displacement

relative to the base.

2.6- Site Selection

The construction sites should be properly selected in accordanoe with the

microzonation criterion. When available sites with active faults, sloping soil profiles.

unclesirable settlement properties ancl possible liquefaction, etc. shoulcl be carefully

evaluated.

2.7- Seismic Joints

Seismic joints shoulcl be provided to separate various parts of buildings and

structures, in particular with different dynamic characteristics, in ortler to allow thern

to vibrate inclependently. Seisrnic joints are provided for buildings with irlcgular plans

an.cl for buildings of non-uniforrn heights. The'width of the joints is deterrnined in such

a way that during the earthquake the parts of the building separated by the joints do not

affeci each othei by collision. Iror rigid buildings with height up to l5m, the minimum

wiclth ol. the seisrnic joints is 25nrm in seisrnic zones I and ll and 40tnrtr in seismic

zone III. For buildings and structures over l5m in height, and for flexible sffuctures.

the joint's width is determined by the following formula:

d > ( 6 r + 6 2 + 1 5 ) ( 2 - l )

But not less than :

25mm for seismic zones l, II:u r r l 40r t t t t t l t l l ' sc is l t t i c z t l t rc l l l

-3-

Wherc:

d - width of. loint (nrrn).

5, , 6z - total lateral cl isplaccrrrcnls ol ' thc two parts ol ' thc brri lcl ing r-utcler thcseisnr ic act ion (scc c lause 4.8) . I ror bu i lc l i r rgs o l 'C lass [ . thcy should bcclctenninecl by dyrrarnic rcsltonsc analysis.

2.8- I i loor St ructurcs

l ; loo l s t t ' r ro t r r rcs s l rou l t l bc < lcs igr rc t l i r r sr rch a way to bc l ravc as r ig i t l l r< l r izont i t lc l iap l r ragrns r r ronol i th ica l ly - jo i r rcc l in a s tnrc tura l systcnr , wl r ich shoLr l r l t rar rsr t t i t la tcra lc I ' f .cc : ts to thc vcr- t ica l s t r t ro tura l systcrn f ior s tnrc t t r lcs not rnc:c l ing l l rc i tb< lvcrcr lu i rcruent , thcy shal l bc t rc i t tcc l as c lc lbr r r ra t r lc s t r t ro tura l c lcr r rcr r ts in thc i r t ra lys is .

- t l -

CI.IAPTER 3 - EVALUATION OF SEISMIC ACTIONS

3.1- General

3.1.1- The seismic analysis of structures shall take the dynamic properties of the

structure irrto consideration either by dynamic arralysis or by equivalent static

alalysis. A dynamic analysis is highly recomrnended for specific structru'es suclt

as slender 6igh-r'ise buildings and structures with irregularitics of geometry or

rnass distribution or rigidity dish'ibution.

Ordilary structures may be designed by the equivalent static rnethod using

colventional linear elastic arralysis. Appropriate post-elastic perfonnance shall be

provided by adequate choice of structural system and ductile detailing. Non-linear'

inethods oi analysis should be employed to veri$r the sequence of inelastic behavior

and the fonnation of collapse mechanisrn.

Notc: If it is cssential tlrat services, e.g. rnecltattical arrd electrical equiprnent and

pipirrgs, rctain their furrctions during ancl after a sevel'e eatthquake, the design o1'

these scrvices sloulcl preferably be done using dynarnic anitlysis procedures

based on the earthquake response of the structdte which supports thern.

r.t.2- Seismic design forces shall be applied at points where rnasses al'e assulned to be

concentrated.

T5e actual mass dishibution may be substituted by a dish'ibution wl'rich simplifies

the analysis without affecting appreciably the fuial results (rnass concentration at floor

levels in multistorey UuitAingi; mass concentrations at an adequate number o1'

equidistant levels in tall consfiuctions like chimneys, towers, etc.) .

For structural design, the directions of seismic actions in horizontal plane should be

taken at least in two ofihogonal directions.

Cantilevers and str-uctures in which vertical seismic effects are significant, shoulcl

be analyzed in the vertical direction taking into accouttt these el-fects.

3.1.3- The rnasses used for analysis have to correspond to the dead and pl'obable live

loads.

For cliffcrclt Classcs of buildings as dcfincd,irt3.2.2, the plobable l ivc load shall be

taken as 50% for sf iuctures ofClassl land25o/oforsf fucturesofCtassl l landClassIV, of floor live loads determined by the existing regulations.

For structures with significant live load such as (Warehouses, Silos, Libraries,

Storage rooms and similar structures), the seismic design forces should be determined

for tG most unfavorable combination of maximum, and / or millimum actual loading.-5 -

Live loads of clatres sltoulcl not be corrsidcrccl for deterntination o1'seisrnic desitrnforces.

Total weight of perrnarrent cquipments should be irrcluded. Snow loads rnay beconsiclered in the calculations at 507o ol' i ts norrnal value.

Wincl lo i tc l sh<lu ld t to t bc considc l 'cc l i r r corn l l i r ra l i r l r r wi th sc isnr ic zrc t i< l r rs .

3..2- Evaluation of Scismic Design [rorces ft lr [ ,)quivalent Static Analysis

' [ 'hc to ta l l tor izorr la l sc is t t t io c lcs igr r for '< ;c aot i r rg orr bu i l r l i r rgs arr r l s t r t rc l r r rcs shal l bc

dctc l ' tn i l tcd accorc l ing to the fb l lowi l rg lor rnul : r , but shal l l ro t bc lcss t l rar r (0 .02W).

Wherc:

V - Total unfactored horizontal seislnic design force.Z - Seismic hazard zoning coef lrc isnt (c lause 3.2.1).I - lmportance factor related to the use of structurc (clausc 3.2.2).S - Dynarnic coefTicicrr t rc latcd to soi l category (clausc 3.2.3).l ( - Structural system coef ic icnt, spcci l icd lbr var ious typcs o1'structures (clausc 3.2.4)W - Total weight of the structure inclucling pcrnranent and probablc livc load

(c la t rsc 3 . 1 .3 and c lz rusc 3 2 .5 ) .

3-.2.1- Scisnric l lazard and Zoning Coefficient - Z

' l -hc cvaluat ior t of scisnr ic hazalc l i r r d i f fcrcnt scis l r r io arcas l i ) r ' thc c lcsign ol '

btri ldilrgs attcl structutes shall bc pcrlblrned according to thc seisrnio zorring rnap o1'I raq (Appcndix A).

The value of coefficientZ is as follows:

Tablc 3.1 - Zoning Cocfficiant Z

Zone Z

0.05

II 0 .07

i l t 0 .09

-6-

- The buildings and structures located in zone 0 need not be designed to satisff the

requir.ements of this code, except for buildings and shuctures of Class I' Forthe

design of buildings and structures of Class I, (clause 3.2.2), il. is necessaryto'deteimile t5e seiimicity of the site by detailed investigations to estimate the design

ald the maxirnum expcctecl earthquakes on tlte basis of the regional and local

seisrnic hazar d investigatiorrs.

3..2.2- Importancc Factor - |

Depending otr ltow Possiblethe inrportance of buildings atldsafety against earthquake. Forfollows:

a damage may affect public safety, and according to

structures, different tcquiretnents shall bc irnposed for'

this reason, buildings and structures are classified as

Class I :

This Class includes all those sfiuctures which are of special importance to the

public, and which must, consequently, not only withstand an eafthquake but remain

opc.atiolal after its occurrencc. The following types of structures form part of this

Clnss:

- St1uctu1es containing toxic or flammable materials and similal installations and

large dams, which require additional safety precautions.

- Hospitals and other medical buildings having surgery and emergency heafinent

facilities.

- Installations dealing with the consequences of disasters, e.g. fire brigades and othet'

vital civil defence centers.

- Buildings and structures related to stand by power generating equipments fol'

essential facilities.

- Structures for cornmunications and tele-communications and other facilities

required for emergency response.

- Tanks or otfuer structures containing, housing or supporting, water or other fire-

suppression materials or equipments required for the protection of hazardous

facilities.

Class II :

This Class includes buildings and structures of high importance to cotnmunity, for

which high level of reliability- is required. The following structures forrn part of this

Class:

-7-

- Water supply installations, water reservoirs and silos.

- Oil attd gas irrstallations, chulrical ;rlarrts, rclincl ' ics, ancl olhcr l i l 'cl inc systcrns.

- Stluctures and installations relatccl to powel genelating stations.

C l lss l l l : . .

This Class ilrcludes buildings atrd structures in whioh relativcly largc number o1'people arc likely to congregate, and which are likely to be endangered to a great degreein t l rc evcnt of carthquake. - fhe fo l lowirrg bui ld i r rgs l 'o l rn part of th is Class.

- High-rise buildings over 6 stories.

- Public buildings of high occupancy rate (greater thzur 300 persons), like mosques.sport buildings, cinema-halls, theah'es, schools, hospitals arrd health facil i t ies.industrial buildings, lnuseunls, l ibraries, and sirnilar cultural buildirrgs.

C l a s s I V :

This Class includes buildings and sfiuctures in which large congregations of peopleare ttot anticillated. The sfructut'es listecl below forrn part of this Class:

- Residential buildittgs, restaurants, warehouses, public builclings, industrial buildingsand all stluctures having occupancies or functions not classified in Classes l, II andI I I .

The value of the importance factor (l) for buildings and sh'uctures of the describedClasses is accordins to Table 3.2 .

Table 3.2 - lmportance Factor - |

Classes of Buildings - Structures Inrportancc Factor - |

Class I 1 . 5 0

Class I I t . 2 5

Class III 1 . 0 0

Class lV 0.75

-8-

3.2.3- Dynanric Coe{ficicnt - S

T[e dynamic coefficient (S) shall be detennined according to diagrarns shown in

Fig.l clepending ort the type of soil profi le as specified in' l"able 3.3 .

\

0.7y1'

4

hlr<{sHtrJ

IL)H€F.a

1.2

LO

0.8

0.6

0.4

0.2

0.0

,1.!o

III

0.00 0.50

Period, T (s)

Fig. 1 S ite-D ep endent N ormalized Resp o nse Sp ectr a

The fundamental period of vibration (T) should be determined using the methods of

stuctural dynamics. In the absence of such calculations the following empirical

formula may be used:

2.501.501.00 4.00

.n 0.09 Ht =' J D (3-2)

For buildings in which lateral force resisting system consists of moment resisting

space frames capable of resisting l00oh of the applied lateral forces, (T) should be

determined bv the formula:

T - 0 .10N (3 -3 )

Whcrc:

T - Fundarnental pedod of vibration of the structure irr thc directionunder consideration (seconds).

H - I{eight of building from ground level (rn).D- The dimension of building in direction parallel to the applied forces (rn).N - l-otal nurnber ol'stories.

The irtfluence of local soil conditions should be taken into account whendetennirring seismic effects on buildings and sh'ucturcs by rncans of dynarnic responscspech-um coefficient depending on the category of ground ullon whiclr tlrc building isto be constructed. The category of soil should be deternrined irccording to theclassification given in Table 3.3 on the basis' of thc results ol ' geotechnicalinvestigations of the constluction site, of engineering, geological, ancl hych'ogeologicaldata, and ol'geophysical and other irrvcstigations of t lre soil l lroli lcs.

3.2.4- Structural systcm cocfficicnt - I(

Sh'uctural systern coefficient (K), takes into account the ductili[, of the structure,the capacity of stress redistribution, the darnping characteristics, and thesupplernentary sh'ength capacity due to the effects that have not been considered in thedesign. Tlte stluctural systettr coefficient (K) depending on the typc ol'tlrc stluctureshould be determined from Table 3.4 .

- t0-

Categoryof

SoilCharacteristics of Soil Profile

Predominant Period of SoilProfile - T"

(Sec.)

I Rock or rock like grounds(crystalline,shell-like and carbonaterocks; limestone, marl stone, well-cemented conglomerate, and similarrock - like rnaterial), very derrse andhard soil deposits cltaracterized byshcar wAvc vclooities V"rnls of thickness less than 60rnconsisting of stable layers of gravel,sand or stiff clay underlayed byfirm and stable geologicalformation.

T* < 0.50 sec.

il Dense to medium dense soildeposits of thickness not more than60m, as well as very dense andhard deposits of thickness over 60mconsisting of stable layers of gravel,sand and stiff to medium stiff claysoverlaying firm geologicalformation.

0.50 sec. ( T, ( 0.75 sec.

III Deposits of low density and softsoil deposits of thickness greaterthan lOrn consisting of loosegravels, saturated loose to mediumdense sands, silty sands (fi'orn soft -plastic to flow plastic), plasticclays, organic soft soils, hydraulic -fill, and other soft and loosernanually back fi l lccl soils with orwithout sandy or other cohesionlessmaterials.

0.75 sec.T.

Table 3.3 - Categories of Soil Profiles

- 1 1 -

Type of the Structure

13uildings with nroment resisting spaceframes with high ductility designedelements.

a)Buildings with ductile momenrresisting space fi'arnes.

b)Buildings with dual systemconsisting of ductile frames andreinforced concrete structural wallsin both directions.

a) Buildings with reinforced concretestructural walls in both directions.

b) Buildings with braced space frames.

a) Masomy buildings strengthenedwith vertical reinforced concretecolumns and horizontal belts.

b) Buildings with reirrforced masonrybearing walls.

c) Slim sh'uctules with srnall dampinsuch as chimneys, water towers, etc.

a Buildings with flexible (soft story)or with an abrupt change in theirstructural rigidity.

b)Unreinforced masonry buildingswith plane concrete walls.

Table 3.4 - Structural Svstem Coefficicnt - l(

3.2.5- Total weight of buildings and structures - (W) shall be considered as theweight on the top of the foundation including probable live load (clause 3.1.3).For structures with rigid basement storey, the weight (W) shall be considereclabove that storev.

- 1 2 -

3.2.6- Influence of soil and foundation conditions

a) Colstruction of buildings and structures in soils susceptible to dynarnic instability

(such as, loose fine sands, soft silt and other soils liable to liquefaction, land and

l.ock slide areas, faulting sites, zrnd sites of expected excessive settlemcttt) should be

avoiclecl. I-lowcvcr if such soil conditions al'e unavoidablc, thc desigrr ancl

construction of buildings ancl shuctures should be based on detailed field and

laboratory dynamic investigations of the foundation materials.

: b) For generally unfavorable soil conditions sufficiently rigid foundations should be

provided taking into consideration the effects of tron-linear deformations of soil

below the entire foundatiorl area.

c) Attention should be paid to the need for confiolling the delbnnation of the

foundations and their influence upon the entire structural system of buildings and

shuctures.

cl) Foundations should be designed so that during seisrnic actiotts excessivedifferential settlemeuts will be avoided.

e) The subgra.de below the entire area of the building should preferably be of the same

typc of soil. Wherevcr this is not possible, suitably locatetl - ioints should bc

provided.

0 For each stluctural unit the foundations should be at the salne lcvel.

g) Isolated footings shall be connected by tie beams in both orthogonal directions. For

strip foundations the tie beam shall be provided in the perpendicular direction.

h) In the case of pile foundations, individual racking piles used as rigid horizontal

bearing rnay produce unfavorable static system. For this reason it is advisable to use

vertical piles only.

3.3- Distribution of Seismic Forces

The total horizontal seismic design force V should be distributed over the height o1'

the building in accordance with the following formula:

W H 1V 1 : v nI wj Irjj = 1

(3-4)

- l 3 -

Where:

V; - lJorizontal seismic design force in i-th level.W.i,Wi - Weight of i-th and j-th floor.Hi.{ - Height of i-th and j-th floor frorn the top of the foundation.

n - Total numbcr of lcvels.

For buildings and structures with more than five levels, 0. l5V shall be corrsidered to bccorrcentrated at the top level while thc rcrnaining 0 B5V shall be distributed in a<;cordance withthc abovc fornrula.

3.3.1- When dynamic response analysis is required, clause 3.3 is not merndatory.

The distribution of seismic design forces in structures which have highly irregularshapes, i.e., large difference irr lateral resistance or in stiffiress betwccn adjacentstories, or other unusual sh'uctural features, should be determined by rnethods o1'dynamic analysis.

3 .3 .2 -Forbu i ld ingsar rds t luc tu res , *he �canbecr i t i ca |(namely cantilevers, prestressed members, or horizontal members with clear'spans greater than 20rn), separate conhol to the vertical seisrnic influence shallbe perforrned considering the relevant vertical scisrnic design force Rcletermined bv the forrnula:

R = O . T Z I S K W P (3-5)

Where:

R - Total vertical seismic design force.Z - Seisrnic lrazard zoning coelficicnt (clause 3.2.1).I - Importance factor (clause 3.2.2).S - Dynamic coefficient related to soil category (clausc 3.2.3).K - Structural system coefficient (clause 3.2.4).Wp - Weight of parts under consideration (clause 3.1.3 and clause 3.2.5).

This force (R) shall be considered in addition to all other relcvant loads exceptwind.

3.3.3- The seisrnic design forces in arry horizontal direction shall be distributed to thevalious elements of the lateral force resisting systern proportiorrally to theirstiffiress, considering the rigidity of the horizontal bracing system or diaphragm.

*14-

3.3.a- [-lorizontal'forsion:rl Moments

Due to arr eccentricity between the cenhe of mass andthe ccntre of'rigidityitis

necessaly to take into account tlre effect of torsional moment at floor levels of the

sfiucture in each direction. The torsional moment (Ti) is calculated ftrr each floor o1'

the sfiucture by the formula:

T 1 : V i ( e i T e ) . . ( 3 - 6 )

Where:

T; - Torsional mornent at the i-th level.Vi - Value of the horizontal fiansverse seismic shear force along each

considered direction separately for the i-th level.e; - Distance between the rigidity centre and the mass cenfi'e at the i-th level'

e - Accidental eccentricity (the effect of nonsynchronous seismic movement along

the building) at thc i-th levcl.The accidental eccentricity (e) is taken as:e : 0.05D - for the usual type of buildings.e : 0.07D - for building with an irregular distribution of structural elements.

D - Dimension of the building perpendicular to the considered direction at the

i-th level.

Thc structr.u'e slrould be designed in such a way that e; [0.15D. ln the case when

this conclit ion oauuot bo satislicd scismio joints should bc providcd. I ior buildings with

more than 7 levels, or buildings with irregular rigiditywhere e;) 0.15D, torsionaleffects should be taken into accoutrt through a three dimensional analysis.

3.3.5- Illernetrts of structures, norrstructural oolnpottetrts and thcir attcltorage shall bcr

desigrred to tesist seismic design force given by the following fonnula:

R e = Z K e %

Where:

R" - Seisrnic design force of elements.Z - Seismic hazard zoning coefficient, (clause 3.2.1).K" - Coefficient related to the type of elements (Table 3.5).W" - Weight of element for which the seismic force is calculated.

(3-7)

- 1 5 -

Talrle 3.5 - Seismic Coefficicnt llelated to thc Blements of Structuresand Non-Structural Components (IQ)

Blements of Structures and Non-Structural Componcnts

Direction ofForcc

Value ofI(.'

Exterior and interior non-bearing walls,partitions and masonry fences.

Normal to lrlatSurface

2 .5

Cantilevers and cantilever palapet walls Normal to FlatSurface

7 . 5

Exterior and interior omamentations andappendages

Any Direction 1 0 . 0

Wlten connected to or a part of a building:towers, tanks, storage racks, chimneys,smoke stacks and penthouses.

Any Direction 2 .5

When comected to or a part of a building:rigid and rigidly mounted equiprnent andt r r i t o h i l r c r y r r o t l ' c t l u i l r : d l i l ' c o l r t i l r r r c d

operation of essential occupancies.

Any HorizontalDirection

2 .5

Wlten resting on the ground: tank pluseffective mass of it's contents.

Any Direction 2 .5

3.4- Method of Dynamic Time History Analysis3.4.1- The dynamic analysis of buildings and structures should be performed for

dctcrmination of the elastic and post-clastic dynarnic rcsl)onsc of thc structure tothe represetttative earthquake ground motions at the site.

'l'he stress and

deformation conditions of buildings and shuctures shall be determined for thecriteria of design and maximum expected earthquake. The acceptable level o1'damages to the sfiuctural atrd non-structural elements for maxiurum expectedearthquakes should be considered.

The seismic analysis by the dynarnic tirne history analysis rnethod is obligatory for'all buildings and structures of Class I .

3.4.2- Eafihquake ground motiotts for dynamic analysis of buildings and sfructuresshould be based on tlte geological, seismic and seismotectonic regional investigationsas well on dynamic investigatiotts of foundation material properties associated with thespecific site. Ground rnotion tirne histories developed for the specific site shall berepresentative of actual earthquake motions.

- 1 6 -

The parameters of ground motion time histories should be determined considering

t6e return period of earthquake occurrence at the site, life-time and usage of buildings'

and sfiuctures arrd the acceptable level of seisrnic risk.

The parameters of grourrd motion time histories should be detennitted for the

criteria of design and the rnaximum expected earthquake.

The dynamic arralysis requires several earthquake time histories, ttl insure adequate

. covel.age of the problem. In the absence of actual strongmotion ealthquake records,"

artificial earthquake ground motions shall be developed on the basis of probabilistic

methods and shall be used as an alternative'

The time history analysis shall be applied to both elastic and inelastic mathematical

rnodel of the structural sYstem.

3.4.3- Whel setting up a rnathernatical model representing the dynamic properties o1'

the rea.l sfiucture, reference should be made to examples of realistic rnodels with

which thc validity ol' thc dynarnic zrnalysis ltas becrt dcrnonstrated.- Considetation should be given to:

a) Cotrpling efl'ccts of thc structurc with its foundation and supllorting grotrtrd'

b) Damping in fundamental and higher modes of vibration; For design purposes, the

darnping ratio for the fundamental mode of regular sfi'uctures is oflen taken as 0.05.

Strucfures that have few sources for fiictional energy dissipation, such as bare

welded steel structures, may posses lower values of damping.

c) Restoring force-distortion relationships of the structural elements in the elastic and

inelastic range.

d) Effects of non-structural elements on the rigidity of the structure.

e) Torsional effects of earthquake response.

For buildings and structures of Class I, where verification of stability is performed

by dynamic tirne history analysis, it is obligatory for flre development of mathematical

models of sh'uctures to use dead plus probable live load (clauses 3.1.3 and 3'2-5)

without load factors.

' 3.4.4- The total horizontal seismic force V obtained by this alalysis sltould not be

smaller thm 75Yo of the design force obtained by the lnethod of equivalent: static analysis (clause 3.2). The total horizontal seismic force should not be

taken smaller than 0.02W.

-17-

CI{APTBII 4 - VBRIFICATION OF STRUCTURAL I}BIIAVIOUR'STRBSS CONDITIONS AND DE FOITMATIONS

The members of buildings and sfiuctures should be designed taking into

consideration the following criteria:

4.1- Pr.oportiotrs of thc scctions ftrr teinforcccl conctctc clctncltts attd cletncnts of steel

strui turcs s l rn l l prc lbrably [ rc <lc lcrnr i r rcr l ot t t l tc l rasis <t f ' thc l i rn i t statc pt ' inciplcs.

,t.z- The design and the control of the buildings and sttuctut'cs and stluctural elements

should be provided using the design methods required by the acceptable design

code of practice.

4.3- The verification of the deformations at limit state is especially necessary for

flexible structures (for example fiame structures of multi-storey buildings where

large deformations would involve some excessive damage to the infill walls and to

thJ other non-strucfural elements, as well as buildings where large horizontal

displacements would cause P-A effects, and an increase of unfavourable effect

such as oscillations of water tanks).

4.4- If calculation is made by the elastic design tlteory, the allowable stresses can beincreased by 33Yo.

4.5- ' l 'hc

allowablc stl 'csscs in thc soil, ftx' thc inost urrfavotrrablc cornbittation o1'

scisrpic arrd othcr cl'fccts, slroulcl bc dctcrlniltccl itt a way that tlrc ltrotor of safcty

agairrst slrcar' ltr i lurc in soil is rrot lcss than ( 1.5). l"ot' sLructul'cs collstructcd in i l

soil proti lc of catcgory l l l , thc laotor ol 'salbty slrall not bc lcss than ( 1.8) .

4.6- I1 the analysis of the structure and structural elements designed by the limit state

theoty, the following load factors should be used:

- For reinforced and prestressed cotrcrete l. lD + L3L I I .4E

but not less than l'30 (D + LR + E)

- For steel shuctures

- For bearing masonry structru'es

1 . 1 5 ( D + L R F E )

1 .50 (D + LR + E )

When live load provide a relieving effect 0.9D + 1.48

- 1 8 -

DLLrr. -E

Wrere:

is the dead load.is the live load.is the probable live load.is the earthquake load.

+.2- Relative Floor DisPlacemcnt:

a) The maximurn relative floor displacement for the seistnic design lbrce of the

structure should not be lalger than

h/200.

Where:

Iri - Heiglrt of the i-th floor.

For buildings and structures with light-weight non-brittle partitions or without

partitions (open frame buildings like shopping centres, garages, etc.), the maximum

ielative flooi displacement for the design seismic force shall not be larger than hi/150.

For ot|er types of builclings and structures, the relative floor displacernent may be

lirnited n""ot:ding to the necessities, depending on the safety and serviceability of

building and life safety of occupants

b) lf for the desigrr of the sh'ucture a dynamic response analysis is perlorrned for thc

purpose of cletennining the behaviour of the structural eletnents in the post-elastic

in.rg., the maximum relative floor displacement for the design seismic action

(Design Earthquake) shall not be larger than h;/150.

c) tn calculating the relative storey displacements, infill walls in frarned structures of

Classes III & IV should not be taken into account.

' For the determination of maximum relative floor displacement, using the method of

equivalent static analysis, the total design lateral seismic force V shall be increased by

the following coefficient:

- For building of Class lll- For building of Class IV

2 .52.0

-t9-

a.7- The maximum horizontal deflection of buildings and structures when determinedfor seisrnic design force shall not be largcr than:

Where:

H - ls the height of the structure above ground.

For industrial and other similar buildings, the maximurn horizontal deflection of thesh'ucture may be larger tlran H/(r00 if tlre stability of tlre building ancl thc structure isanalyti cally and,/or experimental I y con {i nned.

H600

-20-

CHAPTER 5 - CONSTRUCTION OF EARTHQUAKE RESISTANTSTRUCTURES

5.1- Rcinforced Concrete Structures

s.1.1- General, Ductility and Strength llequirements

The post-elastic deformation capacity of reinforced concrete sffuctut'al elements in

practice is measured by the ductility factor, defined as the ratio betr,veen the ultimate

clefor-rnation and the onset of yield. Based on this definition, the tluctility factor o1'

structural cletncltts and thc wholc strtlcturc c:rtt be cvaluatecl.

The procedure for evaluation of ductility and ductility factor is generally difficult

and complicated. It involves two main problems:

I - The estimation of the seismic loading effects by site and seismicity

investigation, andIl' The determination of the mathematical model of structule lbr linear and/or

non-linear dynamic response analysis.

According to this code the ductility requirements are satisfiecl by design and

cletailirrg requirements for structural elements and structutes. (Adclitional dynamic

alalysis is required for structures of Class l). These conditions and requilements are

generally refened to as:

a) Limitation on the use of non-ductile reinforcing steel bars for elements where

ductility capacity is required, especially for sffuctural elements subjected directly to

the seismic actions.

b) For elements subjected to bending or to bending and compression with large

eccentricity, the adoption of appropriate reinforcement percentages and position o1'

reinforcement that will ensure a ductile deformation of elements up to the ultimatelimit state.

c) Ilor elements subjected to cornpression loads with srnall eccentricity, to oompensate

flor low ductility it is necessary to irnplemerrt appropriate design corrditions for the

colcrete in the cross section and percentage of longitudinal and transversereinforcement.

d) Elements subjected to eccentric compression have to be provided with additional

requirernents for sufficient ductility capacity to avoid any type of local failure due

to shear. All critical members including joints, must be checked for a shear force

corresponding to the development of the ultirnate momettts of the sections where

hinges are expected.

-2 t -

e) Plastic hinges developrnent during sever earthquakes iu'e acoeptable only inclclnorts with lr iglr ducti l i ty. l) lastic lr ingcs slroukl bc ai lrrcd to lbrrrr in bcarns ratl tct 'than in colurrtt ts.

I ' Anchoragc ancl sl l l iccs: l{cirr lorocrrrcnt at ori t ical scotions slroulcl bc clctai lcd to.avoid bond failurc.

Steel reinforcing bars with F-, equal to 250,340,410 MPa ale acoeptcd for ductilcsttuctural clemcnts (colurnns, structural walls, bcarns of rn<lrncnt rosist ing f r iuncs, ctc.).Wcldcd wire fabric can be usccl otr ly in horizontal diaphragrns and part ial ly in vert icalstructural walls and shear walls. Generally thesc types o1'rcinforcernerrt arc not used asstructural reinforcement for seismic loads.

5.1.2- Gencral Classi f icat ion

According to the basic structural systern buildings and struotureri arc olassified asfollows:

a) Franre system:A systenr in which both vertical and lateral loads are rcsistccl by spacc ft'atncs.

b) Wall system:A systern in which both vertical and lateral loads are resisted by vertical sh'uctural

walls either single or coupled

c) Dual system:A systern in which vertical loads are mainly carried by space frarne. Resistance to

lateral forces is provided partly by the fi'arne system and partly by structural walls.

5.1.3- Framc Systenrs

Irratnc struoturcs zrrc dcsignecl as structural systcrns irr both <l ircctions of thcbuilding itself. As a rule, the stiffiress of the beams should be srnaller than the stiffiressof the columns, in order to ensure the occurence of non-linear deformations (plastichinges) at the ends of the bearns.

Irrante systetns are designcd in a way tlrat the structural clenrerrts are able todissipate the seisrnic energy by bencling and the occun'ence ol'non-linear tlcfbnnationsat t lrc ertds of the bearns. The tton-l ir tear clefonnations trt the colunrns should beavoidcd.

.

The joints ate designed so that they rernain in the linear range cven after theoccurrence of non-linear deformations irr the elements they join.

-22-

a)Columns: The clesign of columns which are subjected totally or partially to seismici1fluencc should bc bascd olt the following requircmcltt:

PAc -

o" r ; (5- l )

Wrere:

A" - is the gross area of the section of the column (--').

P - is the total axial force in colurnn due to factorecl gravity loads (D+L)

(Newtons)F"u- is the characteristic compressive strength of concrete in (N/mm").

O" - is the reduction coefficient given in Table 5. 1.

r Percentages of total longitudinal reinforcement should fall between the mitrimum

and tnaxirntun lirnits given in Table 5.2.

Tablc 5.1 - Ilcduction Coefficient (Oc)

Type of column Values of O"

Zone I, ll Zone lll

lnterior 0.28 0.2s

Perimeter 0.25 0.22

Comer 0.22 0. r8

- L ) -

Table 5.2 - Pcrccntagc of Minimunr and lVlaximum Longitudin:rlSteel lleinforccment

Colunrn

'fype

Mir r inrurn longi tud inalstcel reinforccments

('%)

Maxinruntlongi tud in: t l s tec l

reinfbrcement ('Yo)

! (MPa) [ (MI 'a)

250 340 4 1 0 250 340 410

lrrtcrior 0 . 8 0.7 0.6 (> 5 4

Pcrirneter 0 .9 0 .8 0 .7 6 5 4

Corncr t . 0 0.9 0 .8 6 5 4

In case when the section of the colurnn is defined by architectura.l reasons, so thatreinforcement is not determined fi'om design considerations, the rninimutn percentageof reinforcement related to the gross concrete section will be consiclercd as 0.57o fol'all types of steel.

It is preferable that the dizuneter of the longitudinal bars may not exoced 32mm andthe distance between centers of bars should not exceed 250rnm.

- Splices: Lap splices, in general, should be away fi'om thc potential hinge regionsarrd be within iu'eas of srnall tensile stresses.

Whcn there are several bars irr a column wlrich are not weldecl, halfoftheselcinlbrcclncnts should bc cxtctrcl [o covcr two l]oors. ' l 'his nlcuns, that 50'lo ol 't l tcrcinftlrcernent are lapped at each floor.

l. 'or structures collstructed in Zone ll l , the lapping of rcinlbroentcrtt with diarneterlarger than 28rnrn, sltould bc rnade by welding.

The design shear force in a colurnn should be cstirnatecl by ultirrrate capacityanalysis with ultimate bending moment at both ends of the oolumn acoording to the[ollowing lbnnula.

1.5 Vic < M"' : M"

h"

-24*

Where:

M,,l,Mu2 - are the ultimatc mornent capacities considered positivc at upper andlower ends of the column under axial load condition (D+l,R).

h" - is the clear height of the column.Vic - is the conhibution of seismic shear force of the colutnn in the i-th floor.

Short colurnrrs with lr"/b [ 2 shoulcl bc avoiclccl.

Wrere:

b - is the dimension of column cross-section in the considered direction.

- The following condition should be satisfied for the cross-section of reinforcedconcrete columns:

A " )M u r * M u 2

(s-3)o. t4h" JL,

All urrits are in (N, m).

Notc: 'fhe

shear coutrol fol columns givert above is obligatory for buildings of Class I.lL III and lV. lrr seismic zones ll arrd lll, in addition to the requirement of IraqrCode 111987 for reinforced concrete.

- The minimurn flarrsverse reinforcement in each direction of the section of thecolurnn should not be less than0.20o/o. The transverse reinforcenrent is calculateclby the following formula:

Apr = - f t oo%. (5-4)" s b

Where:

p r - is the percentage of transverse reinforcement.

Ar - is the total area of ties intersected by a vertical plane parallcl to the side o1'the column (b).

Sb - is the distance between ties.

-25-

hr zones ll and lll within a rninirnurn length of 500nun h'onr the joints, the distzurcetrctwcclr t lrc t ics slrould lr<ll cxoccrl l-5Ornttr iut<l thc pcrcclttagc <ll ' lr i l ttsverscreirrlbrcemcnt of the section of colurnn should not be lcss than 0.25"/.,

'l'lris transversc

reinforcement in the columns should be continued through the joints. Closing of theties is ntade by overlapping extended to the whole length of the shorter sidc.

b) Ilcarns:

- The moment resisting fi'ame systems designed i.n seismic zone il should have

beams with a depth lirnited by the following conditions:

Width of beam ( 0.4 deptlt of bearnWidth of bearn ( 0.5 widtlt of colutnn

- The rnirrinrurn pcrcentage of cornprcssion rcinforccttrcnt (1>') placcd at thc supportshould be:

0.30 p irt scistnic zotte I antl I l0.40 p in seismic zone III.

By more favourable value of the percentages of tensile reinforcement (p) and of

colnpression reinforcement (p'), the ductility of the beam is increased.

The percentage of total longitudinal reinforcement (p+p') should ttot exceed:

45% for steel i fr:250 MPa4.0% for steel i fy:340 MPa3.5o for steel : &:410 MPa

For buildirrgs designed in seismic zone lll, the tnaxitnutn sheitr lbrce in beamsshould be estirnated by the ultimate bending rnoment at eaclt end ol' the beamaccording to the following formula:

Mr , . + M, ,uVn',o* = (5-5)

Also, the following conditions should be satisfied for the cross section of reinforcedconcrete beams:

b dV.u*

+ v ,oL g

(5-6)o.l4 #*

-26-

Where:

Mul,Mun - are the absolute values of the ultimate rnornent capacity at the ends

of the beam.Lr, - is the clear sPan of bearn'Vs - is the shear force frorn (D+Lp).b,d - iu-e the dimensions of the active beam cross-section.f.,u - is the chalacteristic compressive strength of colcrete.

The urrits in the above fonnula are in Newtons and rnillirneters.

- Tle spacitrg of ties in the bcarns near the joints, for a distatrcc equal to double the

leight of the bcam shoukl not exceecl l50tmn, and the atea of stirrups should be at

least O.2o/o. Ln Zone lll, anchorage of the ties should be made by overlapping

extended to the whole length of the shorter side.

c) Joints:

- The joilt's core should be designed in a way that it can transmit the ultimate limit

state forces that can occur in the corurected elements (beams and columns) without

darnage.

- When the width of column is larger than the width of connected beams, all column

reinforcement located outside the core ofjoint is required to interact with the beam.

In tlis case it is preferable to use additional longitudinal reinlbrcernent in the

colutnn tluough the joint.

d) Infi l l Walls:

The infill walls of the frame systems should be made as light as possible. lf by

str.uctural measures and czrlculations, it is proved that it is necessary to have the infill

walls be alchored to the basic system (by special comectol's or joints, etc.), the

arrc6oring of the infill walls should not increase the rigidity of the basic sh'uctural

system.

If the sfiuctural system is flexible, i.e., it can undergo relative deformations at the

floors larger tSan that given in clause 4.7 under seismic effect, the stability and damage

level of infill walls ihould be conf,olled by using experirnental data. The stability of

the infill walls should also be checked for the direction orthogonal to the wall.

according to clause 3.3.5 of this code.

-27-

5.1.4- Wall Systcms

a) Gcncral Design Consir lerations:

- Wall systems arc systerns which have rcinlorccd conct'ete walls as the tnain sfi'uctural

system in both directions.

- All walls, o1 wfiich lateral earthtluake loatl is applied should be dcsigned in such a

way t l rat t l tcy c i t t t d issi l latc scist t t ic c l lc l 'gy l ry l lcxtrral y ic ld i t rg.

- Appropriate design procedures should be usecl to ensure tltat the ultirnate shezu'

rt't"ugllt of walls slrould be in excess of the ltraxitnuttr sltcar force wltcn flexural

strerrgth capacity is reachcd.

- When two or lnore structural walls are inter-contrectecl in the satne plane by

substantially ductile bearns, part of the seismic euergy to be dissipated should be

assigned to the coupling system. Capacity design procedules (non-linear') should be

ur.d to elsul'e that the enelgy dissipation irr the coupling system catr be rnaintained

at its flexural strength capacity. Structural walls, coupled shear walls and

diapluagms should be considered as irrtegtal units.

- The area of the transverse section of the walls, for each ortlrogonal direction should

not be srnaller than I .2o/o of tlte gross floor area of the builditrg.

- ' fhc design ol' walls which arc sub-jected totally or partially to seisrnic influence

should bc bascd olt t l tc lbllowirrg rcqttirclt.tcltt:

PA*=o* fu e -7 )

Whele:

Aw - is the gross area of the horizorrtal section of the wall (rnm2).

f.u - is the characteristic compressive cube strength of concrete (N/mrn2).

Ow - is a coefficient given in Table 5-3.

P - is the total axial force in wall due to gravity loads (D+L) itr (Newton).

Table 5.3 - Valucs of O* for Differcnt Zoncs of Seisrnic Activity

Coefficient Zone I and II Zone lll

(D* 0 . 1 8 0 . r 5

-28-

- The ratio of the total heiglrt to the length of each structural wall slrould not be' srnaller than 2.0 .

- Openings in walls not regularly atranged to form couplecl walls should preferably be

avoided, urrless their influence on thc behaviour of thc wall uttder scislnic action is

either insignificant or accounted for by rational analysis.

- The thickness of the bearing walls should not be less thart l50tnm.

- Bearing walls must be well anchored to floors, roofs, coluntrrs, pilasters, buttresses

arrd intersecting walls.

- [n case of Class I buildings, for which the structural analysis is made by dynamic

procedure in accordance with tlris code, the ultirnatc shczrr forces in the plastio

zones slrould bc ent irely rcsisbd by rcinfbrcctnelt t .

- - l ' hc s l l ' uo l t t t ' : t l w i t l l sys lc t l t t l l t t s l c l t s t l t ' c l l t c g l9 [ : r l

overtunriug.

s la l l i l i t y o l ' t l r c s l t ' t l o l t l t ' c l< r

b) Vertical Reinforcement:

- The ratio of vertical reinforcernent in any part of the section shoulcltrot be less than .0.ZS% or 0.8/f, and not greater tl'm�rn 3.5%o or l6/f, of the cross sectional area of that

part of the *ntt. tf tlre walls are reinforccd with less tharr the above lninimum steel

tlrey should be designed in accordance with the clause 3.2.4, Table 3.4, (Type

No.5) .

- The ratio of the reinforcement at each errd of the wall should not be smaller than

0.15Vo of the total horizontal section of the wall to be placed within a distance ol'

l /10 of thc wall lengtlr at caclr cncl. -fhc Ininittturtr pcrcentagc o[stcel lbr the rniddle

part is 0.15o/o.l 'he middle part may be reinlorccd with wcldcd wire mcslt.

- ' f5e splicing of t lre vcrtical rcinforccrnent irr the nriddle part of t lre wall sectiott rnay

be r1rule by overlapping. Reinforcernent ttt encls trre spliced by weldirrg or the

r,eirrfor.ccnrcnt is extencled ovcr two lloors whiclt rnciuls splicirtg ot'50o/o of t lrc

reinforcernent by overlapping at eaclt level.

c) llorizontal and other lleinforcements:

- The fiorizontal reinforcernent of walls is dcterrnined by calculations, so that the total

calculated seismic shear force for the considered level should tre lesisted by the

horizoltal reinforcemerrt. The horizontal reinforcelnent ratio in any part of the

sectiotr should not be less than 0.25o/o.

-29-

Transverse reinforcement (ties) may be used to confine concrete in legions wherelarge inelastic compressive strains can occul'; to satisfy the intcndcd sectionalductility; and to restrain the vcrtical bars lrorn buckling.

Whcrc diagorral rcinforccrncnt is uscd in coupling bcanrs, thcy slrould lrc cttcloscclby rectangular ties in each directiotr.

5.1.5- Dual Systems

In this system the vertical loads are mainly carried by frames and the resistance tolateral forces is provided partly by the fiame system and partly by the structural walls.

- The distribution of the seismic forces is perfonned according to the deformationcharactedstics of eaclt element of the basic shuctural system.

- The frames should be designed to take at least 25o/oof the total seismic force. Thestructural walls are designed for the value of the shear fbroes obtained by analysisaccording to the requirements of this code.

5.2- Prestressed Concrete Structures

5.2.1- Under the expression prestlessecl corrcrete structure in this oocle it means aconcrctc stlucture in which thc scisrrrio clfccts and tlrc scisrnio cncrgy dissipationis taken by prestressed eletnents. tf the structural clelnents, in addition to thepreshessing steel reinforcement, also contains longitudinal ordinary steelreinforcement of at least 0.457o. such a sfucture is considered as a reinforcedconcrete structure.

- The stability of the system and the elements of the shucture should be proved byanalytical zurd/or experimental procedule.

- The elements of prestressed concrete structures are designed to dissipate the seismicenergy by bending and by the occuffence of non-linear defonnations.

- The prestressed concrete elements in addition to steel tendons for prestressing,slrould contain at least 0.20oh ordinary steel reinforcement to provide for seismicenerbry dissipation

- At the critical sections, where non-linear deformations are expected, closely spacedtransverse reinforcement should be provided to resist the total ultinrate shear force.which comesponds to the ultimate moment in the section increased by l{)"/".

-30-

- The ratio of the total heiglrt to the length of each structural wtrll should not be' srnaller th:rn 2.0 .

- Opepings in walls not regularly arranged to form couplecl walls should preferably be

avoided, unless their influence on the behaviour of thc wall under scislnic action is

either insignificant or accounted for by rational analysis.

- Thc thickness of the bearing walls should ttot be less thatt l5Otnrn.

- Bearing walls must be well anchored to floors, roofs, coluttrns, pilasters, buttresses

arrd intersecting walls.

- [n case of Class I buildings, for which the structural analysis is made by dynamic

procedure in accordance with this code, the ultitnzrte sltczrr forces in the plastio

zones shoulcl bc entirely rcsistctl by rcilrforcctnctlt.

- ' l 'hc s l l r rc l r l r l l wl l l systc l r r l t rusl onsurc l l rc glol ra l s la l l i l i ty o l ' l l lc s l t ' t lo l t l rc l<r

overtuuring.

b) Vertical Reinforcement:

- The ratio of vertical reirrforcement in any part of the section shoultlnot be less than .0.25yo or 0.8/f, and not greater than 3.57o or l6lf, of the cross sectiottal area of thatpart of the wall. If the walls arc reinforced with less tharr tlre abovc tniltimutn steel'tlrey should be designed in accordance with the clause 3.2.4, Table 3.4, (Type

No.5) .

- The ratio of the reinforcement at each end of the wall should not be smaller than

0.15yo of the total horizontal section of the wall to be placed witltitr a distance o1'

l/10 of the wall length at each encl. -l ' lrc rnirt irtturtr pcrcentagc of stecl lbr t lte rniddle

part is 0.I5" . l-he middle part may be reinforced with wcldcd wire mcsh.

- T|e splicing of t lre vertical lcinl 'orccrnent irr the rniddle part ol 't lre wall scction tnay

be nracle by overlappirrg. t leinforcernertt at ettds are spliced by welding or thereipforcelrrcnt is extenclcd ovcr two floors whiclr Incatls splicirtg tt l '5oo/o of thereinforcement by overlapping at each level.

c) llorizontal and other Reinforcements:

- TIre horizontal reinforcernent of walls is dcterrnined by oalculations, so that the total

calculated seismic shear force for the considered level should be lesisted by the

horizontal reinforcernerrt. The horizontal reinforcetnent ratio in any part of the

section should not be less than 0.2504.

-29'

- Transverse reinforcernent (ties) may be used to confine concrete in regions wherelarge irrclastic cornpressive strains can occur'; to satisfy the intcndcd sectionalductility; and to restrain the vcrtical bars finrn buckling.

- Whcrc diagorral rcinforccrncnt is uscd irr coupling bcarns, thcy should lrc ctrcloscdby rectangulal ties in each direction.

5.1.5- Dual Systems

In this system the vertical loads are mainly canied by frames and the resistance tolateral forces is provided partly by the fi'ame system and partly by the stluctural walls.

- The distribution of the seismic forces is performed according to the cleformationcharacteristics of each element of the basic structural system.

- The frames should be designed to take at least 25"/oof the total seismic force. The.structural walls are designed for the value of the shear fbr<;es obtained by analysisaccording to the requirements of this code.

5.2- Prestressed Concrete Structures

5.2.1- Under tlte cxpression presh'essed corrcrcte structurc in this codc it rneans acottcrctc stlucturc in which thc scisnric cl'fccts and thc scisrnic cnct'gy dissipationis taken by prestressed eletnents. lf the stluctural clernents, in addition to theprestressing steel reinforcement, also contains longitudinal ordinary steelreinforcement of at least 0.457o, such a structure is considered as a reinforcedconcrete structure.

- The stability of the system and the elements of the shucture should be proved byanalytical zurd/or experimental procedure.

- The elements of presffessed concrete structures are designed to dissipate the seismicenergy by bending and by the occurrence of non'linear defonnations.

- The prestressed concrete elements in addition to steel tendons for presfiessing,slrould contain at least 0.200 ordinary steel reinforcement to provide for seismicenergy dissipation

- At the critical sections, where non-linear deformations are expected, closely spacedtransverse reinforcement should be provided to resist the total ultimate shear force"wlrich couesponds to the ultirnate moment in the section increased by lO'Yo.

-30-

- The anchorhg of prestressing reinforcement should be outside the expected plastic

hinge zones.

- ,Th" structural defonnations should be restricted dependitrg on the function of the

buildilg and on the effect of the cleformation upon the stluctural elernents of the

building.

5.2.2- Joints of the elements are designed so that:

a) The ultimate strength capacity of the joint should be at least equal to the ultimate

strength of the elements joining into it.

b) Joints should be ductile, assuring ttreir deformability;

c)Joints should be rcinforcccl with aclccluatc shear rcittforccmcltt which should

cornpletely resist the ultirnate sheat force.

5.3- Stecl Structurcs

s.3.1- Steel structlrres should be designecl so that the sttuctural elements are able to

dissipate the seismic energy by bending and by the occunelrce of non-lineat'

cleformations. In case of frame systems, non linear deformations il'e allowed at

the beam ends or at the diagonal bracings.

s.3.2- Local buckling should not be allowed in zones of plastic hinges. Furthermore,

proportioning of the joints should be made so that they provide for the

tansmission of ultimate bendilg moments and the corresponding shear forces

fiom one element to another, without occulrence of non-linear defotmations in

the joint's zone. In other words, the joints should be proportioned to work

always in thc elastic l ' i t l tgc.

s.3.3- In addition to the above, steel sh'uctures must confonn to the following

requirctnents.

a) For one story industrial buildings, the tr ansfer of the forces frorn the roof level is

r-ecornlnelde6 to be through sttucturarl walls or by bracing systems with arr adequate

rigiclity to ensure the lirnitation of the clefomrations within the roof plane. For

strluctlres with more than one storey, vertical strucfural walls or bracings are also

reconunended.

b)Structural solution has to be provided after careful consideratiotr o1'the deformation

cornpatibility of various structural and non-shuctural elernents.

-3 1 -

c) For the support of the principal structut'al elements slides and rollers should be

avoided. In case when such supports are used, measures to lilnit the lateral or.vertical displacements should be considered.

5.4- Prefabricated Structures

5.4.1- The stability of the structural systern and the system ofjoints of prefabricated

reilforced concrete, prestressed and other prefabricated structures, should be

proved by expcrirneutal uttVor analytical study.

5.4.2- The structural system, as well as the system of joints shall be as simple as

possible. The systern of joints between the elemetrts should ensul'e the overall

integrity of tlte structu'e.

s.1.3- The reinforcement that receives the tension stresses should be extended so thatthe yietd stress in the reinforcernent can be developed by atrchorage bond.

5.4.4- The structural floor should be designed as rigid diaphragms in their own planes.

s.4.5- T|1e horizontal joints which join the floor elements, as well as the veftical bearing

elements should be constructed to provide monolithic state of the joints and

stability to the sffuctulal systern iu general.

5.5- Masonry Structures

The basic system of masonry sh'uctures are the bearing walls in both directions o1'

the building, corulected by suffrciently rigid floor systetn. The tetm masottry structures

in this code includes the following:

a) Simple masonry sfructures.

b)Masoruy structures with vertical reinforced concrete elemetrts.

c) Composite masonry and concrete with or without reinforcement.

d)Reinforced masonry sfiuctures with reinforcernent in the joints.

5.5.1- Simple masoffy stuctu'es; are walls of claybricks, blocks, orotltermaterialelements connected with mortar with strength of at least 2.5 N/mm2. It ispreferable to use cement-lime mortar in the coustruction.

-32-

s.5.2- Masonry structures with vertical reinforced concrete elelnents; are walls

consfiucted with masonly units with vefiical reinforced concrete elements casl

in place after the construction of masoruy.

5.5.3- Cornposite masollry arrd concrete with or without reinforcernent; are walls

conitructed with one or two sides of masonry units with a concrete cast insitu

with minimum thickrress of 80rnm. If reinforcernent is used for these walls the

arnount of vertical arrd horizontal rcinforcement is to be estimated by analysis.

l-he rniniruun'l anlount ol ' rcinforoerncnt is 0.lo/oof the total l"hicl<ncss of wall

including masoruY Part'

5.5.4- Iteinforced masoltry structures with reinforcement in thejornts; ttremasonry

walls constructed with mortar of strength of at least 5.0 N/mm2. with steel

reinforcement in horizontal and/or vertical directions. The reinlbrcement shoulcl

be rnade of steel bars placecl at equal distanccs of not tnorc thtrtl 500ttlm.

s.s.s- The walls whicfi provide rigiclity are distributed as urrilbrm as possible in both

clirections of the building considering the following as applicable'

a) The minimum wall thickness is 200nun.

b) The floor slab shall be rigid. If prefabricated elements are used, a topping cast-in-

situ slab with minimum thickness of 40mrn reinforced with steel mesh has to be

used.

c) For structtu.al floors with insufficient rigidity the height of thc building above'ground

shall be lirnited to two levels. These flools can be considered as rigid floors

if cast-in-situ concrete of minimum 40mm reinforced with steel mesh on top is used.

d) The maximum distance between walls which provide rigidity in each direction in

the building should be l0m.

e) T6e width of portions of lltasonry walls between openirlgs when floors ate not

su{I'rcielt ly rigicl shoulclbe at least l13 of stualler opetring cliruettsiorl.

f) Application of cornbined system, i.e., the lower part of the building to be reinforced

coirirete skeleton, ancl the upper part of bearing walls; is not allowed'

g) ln Zone IIl, fi'ee-standing walls arrd parapets above the floor sfiuoture, higher than

800mm, have to be tied together (possibly with reinforced concrete ties).

5.5.6- Checking of the tesistance of masonry struotures is to be made according to the

method of allowable stresses or the limit state method. ln case of buildings with

ratio of height to width over 2.0, the walls should also be checked for bending

and shear, an increase of allswable stresses by 50% is peunitta(t'

-33-

a) tf checking of the resistance is rnade by the rnethocl of allowable stresses, the

prilcipal tinsite shesses in different elements (walls) shall be controlled. The factor

of safety should trot be less than 1.5.

stresses in different elements (walls) shall be obtained from'The principal tensilethe following expression:

o m a (5-8)

Where:

oma- is the allowable principal tensile stress.

xo - is the average shear sfl'ess in the wall elernent due to seisrnic effect.

Oo - is the average stress in the wall elemetrt due to vertical loads'

b) lf checkilg of the resistarrce is rnade by the limit state method, the resistance of the

shucture ihould not bc less than tlre factored total horizontal seismic force

according to clause 3.2 . The load factors are to be irt accordeurce with clause 4'6 .

The resistance of each individual wall element can be calculated according to the

following expressiott:

r- .,o m - -

i l T . ( l 5 t o ) 26 o =

2

t o ttrru o

1 . 5

Where:

onrr - is the principal tensile stress

different rnaterial.

5.5.7- Number of StoreYs

a) The tnaxitnum number of storeysrnasonly structures is given in Table

(5-e)

at failure of walls cottstructed of

inclucling groutrd floor for diflerent systerns o1'

5 . 4 .

o o

-34-

- Tablc 5.4 - Maximum allowcd number of storcys ftrr masonry structures.

Type of Masonry Structurc Scismic Zone

I , l l i l l

a) Simple (clause 5.5.1).aJ 2

b) With vertical reinforced concreteelements (clause 5.5.2).

4 3

c) Cornposite (clause 5.5.3)

- Nou reitrforced

- Reinforced

4

No L imi t *

aJ

No l- i rn i t *

d) Reinforced tnasotny (clause5. 5.4). 5 4

* According to desigu calculations

b) The number of storeys in Table 5.4 rnay be increased if proved by analytical study

with sufficieut experirncntal data.

c) In case masonry buildings are not analyzed for seismic effects, but otherwise

colfonn to th; requirernents of this oode, the allowable nurnber ol' storeys

independerrtly from the structural systetn, is lirnited to:

3 storcys in seismic Zorrc I ancl II-4 storeys in seisrnic Zone ll l .

s.6- Foundations

5.6.1- General

The desigl alcl colshuction of foundatiotrs, foundatiort compollettts, and the

colnection of the superstl'ucture elements thereto, shall confot'ttt to thc rcquirements oi'

t f r is scot ion t t rd ot l rct 'n; l ; l l icablc rct lu i t 'c l t tctr ls i t t Soisrrr ic 7,<tna l , l l ar t r l l l l .

-3 5-

s.6.2- Soil Capacities

The capacity of the foundation soil in bearing or the capacity of the soil interfacebetween pile, pier or caisson nnd thc soil shall be su{ficielrt to support the structurewith all prescribed loads, other than earthquake forces, taking due account of thesettlement that the sffucture is capable of withstanding. For the load combination

inclucling earthquake, the soil capacity must be sufficient to resist loads at acceptablesfiains consiclering both the short tirne of loading and the dynarnic properties of thesoil. Allowable soil stress rnay be increased by rnore thalr 33 percent i[substantiatedby geotechnical data. For piles, this refers to pile capacity as deterrnined by pile-soilf iction or bearing.

5.6.3- Superstructure-to-Foundation Connection

The corurection of supersfluctute elernetrts to the foundation shzrll be adequate toh'ansrnit to the fourdation the forces for which the elernents are designed.

5.6.4- Foundation-Soil Interface

for regular buildings, the force at top of building (0.l5V) as per section 3.3 may be

ornitted when determining the overtuming mornent to be resisted at the foundation-soilinterface.

5.6.5- Special Requirements for Piles and Caissons

a) Piles and caissons shall be designed for flexure whenever tlte top of such tnemberswill be displaced by carthquake rnotions. -l-he criteria and detail ing recluirernents ol 'colunn design by this code shall apply for a length ofsuch tnenrbers equal to 120percent of the flexural lengtlt.

b) Footing hrterconnection

t Pile caps shall be cornpletely interconnected by structural rnembcrs (tie beams) orapproved equivalent rnearts.

2) All strut members shall be capable of resisting in tensiott or compression a forcenot less than l0 percent of the larger footing or column load unless it can beclcrnonstlated that equivalcnt restraint can be proviclecl by other approvcd lneAns.

-36-

AnPendix A

LIST OF REPORTS OF INVESTIGATIONS FOR ELABORATION OF

PRELIMINARY SBISMIC DBSIGN CODB OT IRAQ

1. Volume I, Report IZIIS 88-84. SIESMIC HAZARD EVALUATION AND

SEISMIC ZONING MAPS OF IRAQ.2 Volume II, Report IZIIS 88-85. COMPILATION AND ANALYSIS OF

MICROTREMORS RECORDED IN BAGHDAD.3. Volume IIl, Report IZIIS 88-86.

' GEOTECHNICAL MODELLING OF

SELECTED FREE FIELD AND BUILDING SITES IN BAGHDAD, BASRAH

AND MOSUL, TRANSFER FUNCTION ANALYSIS AND DE'IERMINATION

OF REPRESENTATIVE SOIL PROFILES FOR DYNAMIC SITE RESPONSE

ANALYSIS.4. Volume IV, Report IZIIS 88-87. DYNAMIC PROPER-|IE'S oF THE

REPRESENTATIVE SOIL DEPOSITS IN BAGHDAD.5. Volume v, Report lzlls 88-88. DYNAMIC RESPONSE ANALYSIS OF

nEpRESENTATIVE SOIL PROFILES lN BAGI-IDAD, IIASRAI-I AND MOSUL.

6. Volurne Vl, Iteport lzlls 88-89. PRE,LIMINAI{Y SEISMIC MICI{OZONING OF

BAGHDAD METROPOLII'AN AREA AND EAI{'rllQUAliE DESIGN

SPECTRA.7. Volume VIl, RePort lzlls 88-90.

SCALE AMBIENT VIBRATIONDYNAMTC PROPER:IIES FROM FULL-TESTS OF THE REPRESENTATIVE

BUILDINGS IN BAGHDAD.8 Volume VIIL Report IZIIS 88-91. VERIFICATION CRITERIA BASED ON

SEISMIC STABILIiY ANALYSIS OF BIOLOGICAL RESEARCH CENTRE.

9. Volume IX, Reporl IZIIS 88-92. VERIFICATION CRITERIA BASED ON

SE,ISMIC STEBILTTY ANALYSIS OF APARTMENT BUILDING NO. 15 IN

COMPLEX NO 10 (8 STORIES).l0.volume x, Report IZIIS 88-93. VERIFICATION CRITERIA BASED ON

SEISMIC STABILITY ANALYSIS OF APARTMENT BUILDING tN HAIFA

COMPLEX NO, 8 (16 STORIES).I I Volurne Xl, Report lzlls 88-94. VERIFICATION CltlTERlA IIASED ON

SI i tSMtC S t 'Ad t t , t ' t 'Y nNn l ,YS ls oF coMMr l r ( : l n l . B tJ l l 'D ING IN

JAMUHURIA STREET.12. Volume XII, Report IZIIS 88-95. VERIFICATION CtttTERlA BASED ON

SEISMIC STABILiTY ANALYSIS OF SCHOOL BUILDING IN I1L CAMALIA.

13. Volurne Xlll, Report IZIIS 88-96. EVALUATION OF SOII- ST'RUCTURE

TNTERACTTON dnrnCrs OF SELECTED BUILDINGS AND DYNAMIC

PROPERTIES OF TYPICAL ELEVATED WATER TANK.14. Volume XIV, Report IZIIS 88-97. VULNERABILITY ASSESSEMENT AND

EVALUATION OF ACCEPTABLE SEISMIC RISK.

-37-

15. Volurne XV, Report lzlls 88-98. PRELIMINAIiY DI{AItrT OF II{AQI SEISMICDESTGN CODE (ISDC).

16. Din 4149, Part 1, April 1981, IIUILDING IN GERMAN EARTHQUAKE ZONES,DESIGN LOADS, DIME,NSIONING, DESIGN AND CONSTRUCTION OFCONVENTIONAL BU IL,DINGS.

17. Australian Statrdald, AS 2l2l-1979, AUSTITAI-IAN S'I 'ANDAI{D I"OI{ TI-IEDESIGN OF EARTFIQUAKE-RES ISTANT BUI LDINGS.

18. New Zealand Standalcl . NZS 4203-1976, EAI{TI-IQUAKE l'�ltovlSlONS.l9 lndian Standarcl ISI 1893-1975, CI{11' l l l { lA I tOR l lAl{ ' l ' l lQUAt<Li l t l is ISTANCE

DESIGN OF STRUCTUITES.20. Intemational Standard - ISO 3010- 1988. BASES FOI{ DITSIGN OF

STRUCTURES - SEISMIC ACTIONS ON STRUCTURES.21. UNIFROM BUILDING CODE - 1988 Edition, By lnternational Conference 01:

Building Officials.22. ITECOMMENDED LATEITAL I?OITCE REQUIREMI]NT'S AND

'IENTATIVE

COMMENTARY, By Seisrnology Committee of Structural Engineers Associationof California - 1988.

-3 8-

AI'I'IINDI'X IJ

U R K E Y

\

%

Y

q

- u

l l l

T'- \.4 //

. \

.94

Oo

l 6

It

3 3

. .,/

,(-zt.

4.\

d \O \rL - ' \ . -

4

4 o+

^il

q J 1'1 1 5

SEISMIC ZONING MAP OF IRAQ

1G

Zonc L

o [---l o oo

r ftl1j oos11 L--l o oz

F- -- - l

, r r f f i ooc

"39-

Referenccs :

1- Din 4149, Part l , Apri l l98l, I lui lding in Gennan Earthqual<c Zortes DesignLoacls, Dirnensiorring, Dcsign and Construction ol'Convcntional lSuildings.

2- Australian Standard, AS 2l2l-1979, Australian standard Ibr'l 'hc Design o1'Earthquake - Itesistant Buildings.

3- Ncw Zeland Stanclnrcl, NZS 4203-|979,liarthclual<s l)rovisions.4- Indian Steurdard, lsl I 893- 197 5, Criteria lbr Earthquako Assistarrcc .Design o1'

structures5- International Standard, ISO 3010 - 1988, Bases for Desigm of Structures-

Seisrnic Actions on Structures.6- Unifonn Building Code - 1988, Edition by lnternational Conflerence o1'

Building Offrcials.7- Reconunended Lateral Requirernents and Tentative Cornrncntary, By

Seisrnology Corunittee of Structural Engineerings Association of California -1988 .

-40-