is.1893.1.2002 Criteria for Earthquake Resistant Design

8/12/2019 is.1893.1.2002 Criteria for Earthquake Resistant Design

1/45

Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to

information for citizens to secure access to information under the control of public authorities,in order to promote transparency and accountability in the working of every public authority,

and whereas the attached publication of the Bureau of Indian Standards is of particular interest

to the public, particularly disadvantaged communities and those engaged in the pursuit of

education and knowledge, the attached public safety standard is made available to promote the

timely dissemination of this information in an accurate manner to the public.

!"#$% '(%)

!"# $ %& #' (")* &" +#,-.Satyanarayan Gangaram Pitroda

Invent a New India Using Knowledge

/0)"1 &2 324 #' 5 *)6Jawaharlal Nehru

Step Out From the Old to the New

7"#1&"8+9&"), 7:1&"8+9&")Mazdoor Kisan Shakti Sangathan

The Right to Information, The Right to Live

!"# %& ;


2/45


3/45


4/45

IS 1893 Part 1 ) :2002

Indian StandardCRITERIA FOR EARTHQUAKE RESISTANT

DESIGN OF STRUCTURESPART 1 GENERAL PROVISIONS AND BUILDINGS

( Ffth Revision

ICS 91.120.25

0 BIS 2002


5/45

IS 1893( Part 1 ) :2Indian Standard

CRITERIA FOR EARTHQUAKE RESISTANTDESIGN OF STRUCTURES

PART 1 GENERAL PROVISIONS AND BUILDINGS( Fijth Revision

FOREWORDThis Indian Standard ( Part 1 ) ( Fifth Revision) was adopted by the Bureau of Indian Standards, aflerdraft finalized by the Earthquake Engineering Sectional Committee had been approved by the Civil EngineeDivision Council.Himalayan-Nagalushai region, Indo-GangeticPlain, Western India, Kutch and Kathiawarregions are geologicunstable parts of the country, and some devastating earthquakes of the world have occurred there. A mpart of the peninsular India has also been visited by strong earthquakes, but these were relatively fewnumber occurring at much larger time intervals at any site, and had considerably lesser intensity. The earth@resistant design of structures taking into account seismic data from studies of these Indian earthquakesbecome very essential, particularly in view of the intense construction activity all over the country. Itserve this purpose that IS 1893 : 1962 Recommendations for earthquake resistant design of structurespublished and revised first time in 1966.As a result of additional seismic data collected in India and further knowledge and experience gained sthe publication of the first revision of this standard, the sectional committee felt the need to revise the standagain incorporating many changes, such as revision of maps showing seismic zones and epicentres, and ada more rational approach for design of buildings and sub-structures of bridges. These were covered insecond revision of 1S 1893 brought out in 1970.As a result of the increased use ofthe standard, considerable amount of suggestions were received for modifysome of the provisions of the standard and, therefore, third revision of the standard was brought out in 1The following changes were incorporated in the third revision:

a)

b)c)

d)e)8

The standard incorporated seismic zone factors (previously given asmultiplying factors in the secrevision ) on a more rational basis.Importance factors were introduced to account for the varying degrees of importance for varistructures.In the clauses for design of multi-storeyed buildings, the coefficient of flexibility was given inform of a curve with respect to period of buildings.A more rational formula was used to combine modal shear forces.New clauses were introduced for determination of hydrodynamic pressures in elevated tanks.Clauses on concrete and masonry dams were modified, taking into account their dynamic behaviduring earthquakes. Simplified formulae for design forces were introduced based on results ofextenstudies carried out since second revision of the standard was published.


6/45


7/45

IS 1893( Part 1 ): 2Though the basis for the design of different types of structures is covered in this standard, it is not implthat detailed dynamic analysis should be made in every case. In highly seismic areas, construction of a twhich entails hea~y debris and consequent loss of life and property, such as masonry, particularly mud masoand rubble masonry, should preferably be avoided. For guidance on precautions tobe observed in the constructof buildings, reference maybe made to IS 4326, IS 13827 and IS 13828.Earthquake can cause damage not only on account of the shaking which results from them but also duother chain effects like landslides, floods, fires and disruption to communication. It is, therefore, importantake necessary precautions in the siting, planning and design of structures so that they are safe against ssecondary effects also.The Sectional Committee has appreciated that there cannot bean entirely scientific basis for zoning in vof the scanty data available. Though the magnitudes of different earthquakes which have occurred inpast are known to a reasonable degree of accuracy, the intensities of the shocks caused by these earthquakhave so far been mostly estimated by damage surveys and there is little instrumental evidence to corroborthe conclusions arrived at. Maximum intensity at different places can be fixed on a scale only on the basithe observations made and recorded after the earthquake and thus a zoning map which isbased on the maximintensities arrived at, is likely to lead in some cases to an incorrect conclusion in view of(a) incorrectnessthe assessment of intensities, (b) human error in judgment during the damage survey, and (c) variationquality and design of structures causing variation in type and extent of damage to the structures for the saintensity of shock. The Sectional Committee has therefore, considered that a rational approach to the problwould be to arrive at a zoning map based on known magnitudes and the known epicentres ( see Annexassuming all other conditions as being average and to modifi such an idealized isoseismal map in lightectonics ( see Annex B ), lithology ( see Annex C ) and the maximum intensities as recorded from damsurveys. The Committee has also reviewed such a map in the light of the past history and future possibilitand also attempted to draw the lines demarcating the different zones so as to be clear of important towcities and industrial areas, after making special examination of such cases, as a little modification in the zodemarcations may mean considerable difference to the economics of a project in that area. Maps shownFig. 1and Annexes A, B and C are prepared based on information available upto 1993.In the seismic zoning map, Zone I and II of the contemporary map have been merged and assigned the leof Zone 11. The Killari area has been included in Zone III and necessary modifications made, keeping in vthe probabilistic hazard evaluation. The Bellary isolated zone has been removed. The parts of eastern coareas have shown similar hazard to that of the Killari area, the level of Zone II has been enhanced to Zoneand connected with Zone III of Godawari Graben area.The seismic hazard level with respect to ZPA at 50 percent risk level and 100 years service life goesprogressively increasing from southern peninsular portion to the Himalayan main seismic source, the reviseismic zoning map has given status ofZone III toNarmada Tectonic Domain, Mahanandi Graben and GodawGraben. This is a logical normalization keeping in view the apprehended higher strain rates in these domaon geological consideration of higher neotectonic activity recorded in these areas.Attention is particularly drawn to the fact that the intensity of shock due to an earthquake could vary locaat anyplace due to variation in soil conditions. Earthquake response of systems would be affected by differtypes of foundation system in addition to variation of ground motion due to various types of soils. Considerthe effects in a gross manner, the standard gives guidelines for arriving at design seismic coet cients baon stiffness of base soil.It is important to note that the seismic coefficient, used in the design of any structure, is dependent on navariable factors and it is an extremely difficult task to determine the exact seismic coefficient in each givcase. It is, therefore, necessa~ to indicate broadly the seismic coefficients that could generally be adop


8/45

IS 1893( Part 1 ) :2002accuracy either on a deterministic or on a probabilistic basis. The basic zone factors included hereinreasonable estimates of effective peak ground accelerations for the design of various structures coveredthis standard. Zone factors for some important towns are given in Annex E.Base isolation and energy absorbing devices may be used for earthquake resistant design. Only standadevices having detailed experimental data on the performance should be used. The designer must demonstrby detailed analyses that these devices provide sufficient protection to the buildings and equipment as envisagin this standard. Performance of locally assembled isolation and energy absorbing devices should be evaluaexperimentally before they are used in practice. Design of buildings and equipment using such device shobe reviewed by the competent authority.Base isolation systems are found usefhl for short period structures, say less than 0.7s including soil-structuinteraction.In the formulation of this standard, due weightage has been given to international coordination amongstandards and practices prevailing in different countries in addition to relating it to the practices in the fiin this country. Assistance has particularly been derived from the following publications:

a) UBC 1994, Uniform Building Code, International Conference ofBuilding Officials, Whittier, CkdifomU.S.A.1994.b) NEHRP 1991, NEHRP Recommended Provisions for the Development of Seismic Regulations for NBuildings,Part 1: Provisions,ReportNo. FEMA 222,FederalEmergencyManagement Agency,WashingD.C., U.S.A., January 1992.

c) NEHRP 1991, NEHRP Recommended Provisions for the Development of Seismic Regulations for NBuildings, Part 2: Commentary, Report No. FEMA 223, Federal Emergency Management AgenWashington, D.C., U.S.A., January 1992.

d) NZS 4203:1992, Code of Practice for General Structural Design and Design Loadings for BuildinStandards Association of New Zealand, Wellington, New Zealand, 1992.

In the preparation of this standard considerable assistance has been given by the Department of EarthquaEngineering, University of Roorkee; Indian Institute of Technology, Kanpuq IIT Bombay, Mumbai; GeologSurvey of India; India Meteorological Department, and several other organizations.The units used with the items covered by the symbols shall be consistent throughout this standard, unlspecifically noted otherwise.The composition of the Committee responsible for the formulation of this standard is given in Annex F.For the purpose of deciding whether a particular requirement of this standard is complied with, the final vaobserved or calculated, expressing the result of a test or analysis, shall be rounded off in accordance wIS 2:1960 Rules for rounding off numerical values ( revised ). The number of signflcant places retainedthe rounded off value should be the same as that of the specified value in this standard.


9/45


10/45


11/45


12/45

IS 1893( Part ) :2 00 23 TERMINOLOGY FOR EARTHQUAKEENGINEERING3.1 For the purpose of this standard, the followingdefinitions shall apply which are applicable generallyto all structures.

NOTE For the definitions of terms pertaining to soilmechanics and soil dynamics references may be madeto IS 2809 and IS 2810.

3.2 Closely-Spaced ModesClosely-spaced modes of a structure are those of itsnatural modes of vibration whose natural frequenciesdiffer from each other by 10 percent or less of thelower frequency.3.3 Critical DampingThe damping beyond which the free vibration motionwill not be oscillatory.3.4 DampingThe effect of internal friction, imperfect elasticity ofmaterial, slipping, sliding, etc in reducing the amplitudeofvibration and is expressed as a percentage of criticaldamping.3.5 Design Acceleration SpectrumDesign acceleration spectrum refers to an averagesmoothenedplot ofmaximum acceleration as a fimctionof frequency or time period of vibration for a specitleddamping ratio for earthquake excitations at the baseof a single degree of freedom system.3.6 Design Basis Earthquake ( DBE )It is the earthquake which can reasonably be expectedto occur at least once during the design life of thestructure.3.7 Design Horizontal Acceleration CoefficientAh)It is a horizontal acceleration coefficient that shall beused for design of structures.3.8 Design Lateral ForceIt is the horizontal seismic force prescribed by thisstandard, that shall be used to design a structure.3.9 Ductility

3.11 Effective Peak Ground Acceleration ( EPGAIt is O.4times the 5 percent damped average spectraacceleration between period 0.1 to 0.3 s. This shabe taken as Zero Period Acceleration ( ZPA ).3.12 Floor Response SpectraFloor response spectra is the response spectra fortime history motion of a floor. This floor motion timhistory is obtained by an analysis of multi-storeybuilding for appropriate material damping valuesubjected to a specified earthquake motion at the basof structure.3.13 FocusThe originating earthquake source ofthe elastic wavinside the earth which cause shaking of ground duto earthquake.3.14 Importance Factor (1)It is a factor used to obtain the design seismic forcdepending on the functional use of the structurecharacterised by hazardous consequences of its failurits post-earthquake functional need, historic valueor economic importance.3.15 Intensity of EarthquakeThe intensity of an earthquake at a place is a measurof the strength of shaking during the earthquake, anis indicated by a number according to the modifiedMercalli Scale or M.S.K. Scale of seismic intensitie(see AnnexD ).3.16 LiquefactionLiquefaction is a state in saturated cohesionless sowherein the effective shear strength is reducednegligible value for all engineering purpose due tpore pressure caused by vibrations during aearthquake when they approach the total confiningpressure. In this condition the soil tends to behavlike a fluid mass.3.17 Lithological FeaturesThe nature of the geological formation of the earthcrust abovebed rock on the basis of such characteristicas colour, structure, mineralogical composition angrain size.3.18 MagnitudeofEarthquake ( Richter MagnitudeThe magnitude of earthquake is a number, which is


13/45

3.19 Maximum Considered Earthquake ( MCE )The most severe earthquake effects considered bythis standard.3.20 Modal Mass ( lf~ )Modal mass of a structure subjected to horizontal orvertical, as the case maybe, ground motion is apartofthe total seismic mass of the structure that is effectivein mode k of vibration. The modal mass for a givenmode has a unique value irrespective of scaling ofthe mode shape.3.21 Modal Participation Factor (Pk)Modal participation factor of mode k of vibration isthe amount by which mode k contributes to the overallvibration of the structure under horizontal and verticalearthquake ground motions. Since the amplitudes of95 percent mode shapes can be scaled arbitrarily, thevalue of this factor depends on the scaling used formode shapes.3.22 Modes of Vibration ( see Normal Mode)3.23 Mode Shape Coefficient ( i~)When a system is vibrating in normal mode k, at anyparticular instant of time, the amplitude of massi expressed as a ratio of the amplitude of one of themasses of the system, is known as mode shapecoefficient ( @i~.3.24 Natural Period (T)Natural period of a structure is its time period ofundamped free vibration.3.24,1 Fundamental Natural Period ( T1)It is the first ( longest ) modal time period of vibration.3.24.2 Modal Natural Period ( T~)The modal natural period of mode k is the time periodof vibration in mode k.3.25 Normal ModeA systemis said to be vibrating in a normal mode whenall its masses attain maximum values of displacementsand rotations simultaneously, and pass throughequilibrium positions simultaneously.

IS 1893 Part 1 ) :20idealized single degree freedom systemshaving cerperiod and damping, during earthquake gromotion. The maximum response is plotted againstundamped natural period and for various dampvalues, and can be expressed in terms of maximabsolute acceleration, maximum relative velocitymaximum relative displacement.3.28 Seismic MassIt is the seismic weight divided by accelerationto gravity.3.29 Seismic Weight (W)It is the total dead load plus appropriate amountspecified imposed load.3.30 Structural Response Factors ( S,/g )It is a factor denoting the acceleration respospectrum of the structure subjected to earthquground vibrations, and depends on natural peof vibration and damping of the structure.3.31 Tectonic FeaturesThe nature of geological formation of the bedrockthe earths crust revealing regions characterizedstructural features, such as dislocation, distortifaults, folding, thrusts, volcanoes with their agformation, which are directly involved in the emovement or quake resulting in the abconsequences.3.32 Time History AnalysisIt is an analysis ofthe dynamic respmse ofthe strucat each increment of time, when its base is subjeto a specific ground motion time history.3.33 Zone Factor (Z)It is a factor to obtain the design spectrum dependon the perceived maximum seismic risk characterby Maximum Considered Earthquake ( MCE ) inzone in which the structure is located. The basicfiwtorsincluded in this standard are reasonable estiof effective peak ground acceleration.3.34 Zero Period Acceleration ( ZPA )It is the value of acceleration response spectrumperiod below 0.03 s ( frequencies above 33 Hz)-,.4 TERMINOLOGY FOR EARTHQUAKE


14/45

IS 1893( Part 1 ) :20024.3 Base Dimensions (d)Base dimension of the building along a direction isthe dimension at its base, in metre, along that direction.4.4 Centre of MassThe point through which the resultant of the massesof a system acts. This point corresponds to the centreof gravity of masses of system.4.5 Centre of StiffnessThe point through which the resultant ofthe restoringforces of a system acts.4.6 Design Eccentricity ( e~i)It is the value of eccentricity to be used at floor i intorsion calculations for design.4.7 Design Seismic Base Shear ( V~)It is the total design lateral force at the base of astructure.4.8 DiaphragmIt is a horizontal, or nearly horizontal system, whichtransmits lateral forcesto thevertical resisting elements,for example, reinforced concrete floors and horizontalbracing systems.4.9 Dual SystemBuildings with dual system consist of shear walls( orbraced frames ) and moment resisting frames suchthat:

a) The two systems are designed to resist thetotal design lateral force in proportion to theirlateral stiffness considering the interactionof the dual system at all floor levels; and

b) The moment resisting frames are designedto independently resist at least 25 percentof the design base shear.

4.10 Height of Floor ( hi )It is the difference in levels between the base of thebuilding and that of floor i.4.11 Height of Structure(k)It is the difference in levels, in metres, between itsbase and its highest level.4.12 Horizontal Bracing System

4.14 Lateral Force Resisting ElementIt is part of the structural system assigned to resistlateral forces.4.15 Moment-Resisting FrameIt is a frame in which members and joints are capableof resisting forces primarily by flexure.4.15.1 Ordinary Moment-Resisting FrameIt is a moment-resisting frame not meeting specialdetailing requirements for ductile behaviour.4.15.2 Special Moment-Resisting FrameIt is a moment-resisting frame specially detailedto provide ductile behaviour and comply withthe requirements given in IS 4326 or IS 13920 oSP6(6).4.16 Number of Storeys ( n )Number of storeys of a building isthe number of levelabove the base. This excludes the basement storeyswhere basement walls are connected with the groundfloor deck or fitted between the building columns. Butit includes the basement storeys, when they are noso connected.4.17 Principal AxesPrincipal axes ofa building are generally two mutuallyperpendicular horizontal directions inphmof abuildingalong which the geometry of the building is oriented4.18 P-A EffectIt is the secondary effect on shears and moments oframe members due to action of the vertical loadsinteracting with the lateral displacement ofbuildingresulting from seismic for~es.4.19 Shear WallIt is a wall designed to resist lateral forces acting inits own plane.4.20 Soft StoreyIt is one in which the lateral stiffness is less than70 percent of that in the storey above or less than80 percent of the average lateral stiffness ofthe threstoreys above.4.21 Static Eccentricity ( e~l)It is the distance between centre of mass and centreof rigidity of floor i.


15/45

4.24 Storey Shear ( ~)It is the sum of design lateral forces at all levels abovethe storey under consideration.4.25 Weak StoreyIt is one in which the storey lateral strength is lessthan 80 percent of that in the storey above, The storeylateral strength is the total strength of all seismic forceresisting elements sharing the storey shear in theconsidered direction.5 SYMBOLSThe symbols and notations given below apply to theprovisions of this standard:

.4 hA~

bi

cd

DLdl

eS1

ELX

ELYEL,

FroofFi

?

Design horizontal seismic coefficientDesign horizontal acceleration spectrumvalue for mode kof vibrationithFloor plan dimension of the buildingperpendicular to the direction of forceIndex for the closely-spaced modesBase dimension ofthe building, in metres,in the direction in which the seismic forceis considered.Response quantity due to dead loadDesign eccentricity to be used at floor icalculated as per 7.8.2Static eccentricity at floor i defined as thedistance between centre ofmass and centreof rigidityResponse quantity due to earthquake loadfor horizontal shaking along x-directionResponse quantity due to earthquake loadfor horizontal shaking along y-directionResponse quantity due to earthquake loadfor vertical shaking along z-directionDesign lateral forces at the roof due to allmodes consideredDesign lateral forces at the floor i due toall modes consideredAcceleration due to gravity

nNPkQ,Q~~r

RSa/g

T

~

Tk

T1

VBpB

q

qkv roof

wWizOi k

a

IS 1893( Part 1) :20Number of storeysSPT value for soilModal participation factor of mode kLateral force at floor iDesign lateral force at floor i in modeNumber of modes to be considered as7.8.4.2Response reduction factorAverage response acceleration coefficifor rock or soil sites as given by Figand Table 3 based on appropriate natuperiods and damping of the structureUndamped natural period of vibrationthe structure (in second )Approximate fundamental period (seconds )Undamped natural period of mode kvibration (in second )Fundamental natural period of vibrati(in second )Design seismic base shearDesign base shear calculated usingapproximate fimdamental period T,Peak storey shear force in storey i dueall modes consideredShear force in storey i in mode kPeak storey shear force at the roof dueall modes consideredSeismic weight of the structureSeismic weight of floor iZone factorMode shape coet cient at floor i in mokPeak response (for example member forcdisplacements, storey forces, storey sheor base reactions ) due to all modconsidered


16/45

IS 1893( Part 1 ) :2002Pi j Coefficient used in the Complete QuadraticCombination ( CQC ) method whilecombining responses of modes i andjoi Circular frequency in rad/second in the

iti mode6 GENERAL PRINCIPLES AND DESIGNCRITERIA6.1 General Principles6.1.1 Ground MotionThe characteristics ( intensity, duratio~ etc ) of seismicground vibrations expected at any location dependsupon the magnitude of earthquake, its depth of focus,distance from the epicentre, characteristics of the paththrough which the seismic waves travel, and the soilstrata on which the structure stands. The randomearthquake ground motions, which cause the structureto vibrate, can be resolved in any three mutuallyperpendicular directions. The predominant directionof ground vibration is usually horizontal.Earthquake-generated vertical inertia forces are to beconsidered in design unless checked and proven byspecimen calculations to be not significant. Verticalacceleration should be considered in structures withlarge spans, those in which stability is a criterion fordesign, or for overall stability analysis of structures.Reduction in gravity force due to vertical componentof ground motions can be particularly detrimental incases of prestressed horizontal members and ofcantilevered members. Hence, special attention shouldbe paid to the effectofvertical component of the groundmotion on prestressed or cantilevered beams, girdersand slabs.6.1.2 The response of a structure to ground vibrationsis a fimction of the nature of foundation soil; materials,form, size and mode of construction of structures;and the duration and characteristics of ground motion.This standard specifies design forces for structuresstanding on rocks or soils which do not settle, liquefior slide due to lossof strength during ground vibrations.6.1.3 The design approach adopted in this standardis to ensure that structures possess at least a minimumstrength to withstand minor earthquakes (


17/45

IS 1893( Part 1 ): 2b) An addition that is not structurallyindependent from an existing structure shallbe designed and constructed such thatthe entire structure conforms to the seismicforce resistance requirements for new

structures unless the following threeconditions are complied with:1)2)

3)

The addition shall comply with therequirements for new structures,The addition shall not increase the seismicforces in any structural elements of theexisting structure bymore than 5percentunless the capacity of the elementsubject to the increased force is still incompliance with this standard, andThe additicn shall not decrease theseismic resistance of any structuralelement of the existing structure unlessreduced resistance is equal to or greaterthan that required for new structures.

6.1.8 Change in OccupancyWhen a change of occupancy results in a structurebeing re-classified to a higher importance factor ( 1 ),the structure shall conform to the seismic requirementsfor anew structure with the higher importance factor.6.2 AssumptionsThe following assumptions shall be made in theearthquake resistant design of structures:

a)

b)

c)

Earthquake causes impulsive ground motions,which are complex and irregular in character,changing in period and amplitude each lastingfor a small duration. Therefore, resonance ofthe type as visualized under steady-statesinusoidal excitations, will not occur as itwould need time to buildup such amplitudes.NOTE However, there are exceptions whereresonance-like conditions have been seen to occurbetween long distance waves and tall structuresfounded on deep soft soils.Earthquake is not likely to occursimultaneously with wind or maximum floodor maximum sea waves,The value of elastic modulus of materials,

these shall be combined as per 6.3.1.1 and 6.3where the terms DL, IL and EL stand for the respoquantities due to dead load, imposed loaddesignated earthquake load respectively.6.3.1.1 Load factors for plastic design of sstructuresIn the plastic design of steel structures, the followload combinations shall be accounted for:

1) 1.7( DL.+IL )2) 1.7( DL*EL)3) 1.3( DL+lL*EL)

6.3.1.2 Partial safety factors for limit state desof reinforced concrete and prestressed concrstructuresIn the limit state design of reinforced and prestresconcrete structures, the following load combinatishall be accounted for:

1) 1.5( DL+lL)2) 1.2( DL+ZL+EL)3) 1.5( DL+EL)4) 0.9DL* 1.5EL

6.3.2 Design Horizontal Earthquake Load6.3.2.1 When the lateral load resisting elementsoriented along orthogonal horizontal direction,structure shall be designed for the effects due todesign earthquake load in one horizontal directiotime.6.3.2.2 When the lateral load resisting elementsnot oriented along the orthogonal horizontal directithe stmcture shall be designed for the effects dufoil design earthquake load in one horizontal direcplus 30 percent of the design earthquake load inother direction.

NOTE For instance, the building should be desifor ( + ELx i 0.3 EL.y ) as well as ( * 0.3 ELx * Ewhere x and y are two orthogonal horizontal directiEL in 6.3.1.1 and 6.3.1,2 shall be replaced by ( E0.3 ELy ) or ( ELy i 0.3 . Lh ).

6.3.3 Design Vertical Earthquake Load


18/45

IS 1893( Part 1 ) :2002assumption that when the maximum response fromone component occurs, the responses from the othertwo component are 30 percent of their maximum. Allpossible combinations of the three components (ELx,ELy and ELz ) including variations in sign ( plus orminus ) shall be considered, Thus, the response dueearthquake force (EL ) is the maximum ofthe followingthree cases:

1) ELX*O.3 ELyho.3ELz2) *ELy*O.3 ELx&O.3 ELz3) *ELz* 0.3 ELx&O.3 ELy

where x and y are two orthogonal directions and z isvertical direction.6.3.4.2 As an alternative to the procedure in 6.3.4.1,the response (EL ) due to the combined effect of thethree components can be obtained on the basis ofsquare root of the sum of the square ( SRSS ) thatis

EL = ~ (ELx)2+ (ELy)z+(ELz)2NOTE The combination procedure of 6.3.4.1 and6.3.4.2 apply to the same response quantity (say, momentin a column about its major axis, or storey shear in aframe) due to different components ofthe ground motion.

6.3.4.3 When two component motions ( say onehorizontal and one vertical, or only two horizontal)are combined, the equations in 6.3.4.1 and 6.3.4.2should be modified by del >tingthe term representingthe response due to the component ofmotion not beingconsidered.6.3.5 Increase in Permissible Stresses6.3.5.1 Increase impermissible stresses in materialsWhen earthquake forces are considered along withother normal design forces, the permissible stressesin material, in the elastic method of design, maybeincreased by one-third. However, for steels having adefinite yield stress, the stress be limited to the yieldstress; for steels without a definite yield point, thestress will be limited to 80 percent of the ultimatestrength or 0.2 percent proof stress, whichever issmaller; and that in prestressed concrete members,the tensile stressin the extreme fibers of the concretemay be permitted so as not to exceed two-thirds ofthe modulus of rupture of concrete.6.3.5.2 Increase in allowable pressure in soils

Zones III, IV, V and less than 10 in seismic Zonethe vibration caused by earthquake may cauliquefaction or excessive total and differentisettlements. Such sites should preferably be avoidwhile locating new settlements or important projeOtherwise, this aspect of the problem needs toinvestigated and appropriate methods of compactior stabilization adopted to achieve suitable N-valas indicated in Note 3 under Table 1. Alternativeldeep pile foundation may be provided and takendepths well into the layer which is not likely to liqueMarine clays and other sensitive clays are also knoto lique~ due to collapse of soil structure and wneed special treatment according to site condition

NOTE Specialist literature may be referreddetermining liquefaction potential of a site.

6.4 Design Spectrum6.4.1 For the purpose of determining seismic forcthe country is classified into four seismic zonesshown in Fig. 1.6.4.2 The design horizontal seismic coefficientfor a structure shall be determined by the followiexpression:

.zIsaAh=2RgProvided that for any structure with T


19/45


20/45

S-1893 ( Part 1 ) :2002for rock or soil sites as given by Fig. 2 andTable 3 based on appropriate natural periodsand damping of the structure. These curvesrepresent free tleld groundmotion.NOTE For various types of structures, thevalues of Importance Factor I, Response ReductionFactor R, and damping values are given in therespective parts of this standard. The method( empirical or otherwise ) to calculate the naturalperiods ofthe structure to beadopted for evaluatingS,/g is sdso given in the respective parts of thisstandard.

Table 2 Zone Factor, Z( Clause 6.4.2)

Seismic II 111 Iv vZone

Seismic Low Moderate Severe VeryIntensity Severe

z 0.10 0.16 0,24 0.366.4.3 Where a number of modes are to be consideredfor dynamic analysis, the value of Ah as definedin 6.4.2 for each mode shall be determined using thenatural period of vibration of that mode.6.4.4 For underground structures and foundationsat depths of 30 m or below, the design horizontalacceleration spectrum value shall be taken as half thevalue obtained from 6.4.2. For structures and

3.0

2.52.0

1.5

1.0

foundations placed between the ground level and30m depth, the design horizontal acceleration spectrumvalue shall be linearly interpolated between Ah and0.5 Ah, where Ah is as specified in 6.4.2.6.4.5 The design acceleration spectrum for verticalmotions, when required, may be taken as two-thirdsofthe design horizontal acceleration spectrum specitledin 6.4.2.Figure 2 shows the proposed 5 percent spectra forocky and soils sites and Table 3 gives the multiplyingfactors for obtaining spectral values for various otheclampings.For rocky, or hard soil sites

-1

1+15~ 0.00< Tso.los,g = 2.50 O.1O


21/45

6.4.6 In case design spectrum is specifically preparedfor a structure at a particular project site, the samemay be used for design at the discretion of the projectauthorities7 BUILDINGS7.1 Regular and Irregular ConfigurationTo perform well in an earthquake, a building shouldpossess four main attributes, namely simple and regularcotilguration, and adequate lateral strength, stiffnessand ductility. Buildings having simple regolar geomet~and uniformly distributed mass and stiffness in planas well as in elevation, suffer much less damage thanbuildings with irregular configurations. A buildingshall be considered as irregular for the purposes ofthis standard, if at least one of the conditions givenin Tables 4 and 5 is applicable,7.2 Importance Factor Zand Response ReductionFactorRThe minimum value of importanm factor,1, for ditlerentbuilding systems shall be as given in Table 6. Theresponse reduction factor, R, for different buildingsystems shall be as given in Table 7.7.3 Design Imposed Loads for Earthquakes ForceCalculation7.3.1 For various loading classes as specified inIS875( Part 2 ), the earthquake force shall be calculatcxlfor the full dead load plus the percentage of imposedload as given in Table 8.7.3.2 For calculating the design seismic forces ofthestructure, the imposed load on roof need not beconsidered.7.3.3 The percentage of imposed loads given in 7.3.1and 7.3.2 shall also be used for Whole frame loadedcondition in the load combinations specified in 6.3.L 1

IS 1893( Part 1 ): 2002and 6.3.1.2 where the gravity loads are combined withthe earthquake loads [ that is, in load combinations(3) in 6.3.1.1, and (2) in 6.3.1.2 ]. No further reductionin the imposed load will be used as envisaged inIS 875( Part 2 ) for number of storeys above the oneunder consideration or for large spans of beams orfloors.7.3.4 The proportions of imposed load indicated abovefor calculating the lateral design forces for earthquakesare applicable to average conditions. Where theprobable loads at the time of earthquake are moreaccurately assessed, the designer may alter theproportions indicated or even replace the entireimposed load proportions by the actual assessed load.In such cases, where the imposed load is not assessedas per 7.3.1 and 7.3.2 only that part of imposed load,which possesses mass, shall be considered. Lateraldesign force for earthquakes shall not be calculatedon contribution of impact effects from imposed loads.7.3.5 Other loads apart from those given above ( forexample snow and permanent equipment ) shall beconsidered as appropriate.7.4 Seismic Weight7.4.1 Seismic Weight of FloorsThe seismic weight of each floor is its full dead loadplus appropriate amount of imposed load, as specifiedin 7.3.1 and 7.3.2. While computing the seismic weightof each floor, the weight of columns and walls in anystorey shall be equally distributed to the floors aboveand below the storey.7.4.2 Seismic Weight of BuildingThe seismic weight of the whole building is the sumof the seismic weights of all the floors.7.4.3 Any weight supported in between storeys shallbe distributed to the floors above and below in inverseproportion to its distance from the floors.

Table 3 Multiplying Factors for Obtaining Values for Other Damping( Clause 6.4.2)

Damping, o 2 5 7 10 15 20 25 30percentFactors 3.20 1,40 1.00 0.90 0 .80 0.70 0,60 0 .55 0 .50


22/45

IS 1893( Part 1 ) :2002Table 4 Definitions of Irregular Buildings Plan Irregularities ( Fig. 3 )

( Clause 7.1 )S1 No.(1)i)

ii)

iii)

iv)

v)

Irregularity Type and Description(2)

Torsion IrregularityTo be considered when floor diaphragms are rigidin their own plan in relation to the vertical structuralelements that resist the lateral forces. Torsionalirregularity to be considered to exist when themaximum storey drift, computed with designeccentricity, at one end of the structures transverseto an axis is more than 1.2 times the average ofthe storey drifts at the two ends of the structureRe-en?rant CornersPlan configurations of a structure and its lateralforce resisting system contain re-entrant corners,where both projections of the structure beyond there-entrant corner are greater than 15 percent ofits plan dimension in the given directionDiaphragm DiscontinuityDiaphragms with abrupt discontinuities or variationsin stiffness, including those having cut-out or openareas greater than 50 percent of the gross encloseddiaphragm area, or changes in effective diaphragmstiffness of more than 50 percent from one storeyto the nextOut-of-Plane OffsetsDiscontinuities in a lateral force resistance path,such as out-of-plane offsets of vertical elementsNon-parallel SystemsThe vertical elements resisting the lateral forceare not parallel to or symmetric about the majororthogonal axes or the lateral force resisting elements

Table 5 Definition of Irregular Buildings Vertical Irregularities ( Fig. 4 )( Clause 7.1 )

S1 No. Irregularity Type and Description(1) (2)i) a) Stiffness Irregularity Soft Storey

A soft storey is one in which the lateral stiffnessis less than 70 percent of that in the storey aboveor less than 80 percent of the average lateral stiffnessof the three storeys aboveb) Stiffness Irregularity Extreme Soft StoreyA extreme soft storey is one in which the lateral

Table 5 ConcludedS1 No.(1)ii)

iii)

iv)

v

Irregularity Type and Description(2)

Mass Irregulari@Mass irregularity shall be considered to exist whthe seismic weight of any storey is more thanpercent ofthat of its adjacent storeys. The irregulaneed not be considered in case of roofsVertical Geometric IrregularityVertical geometric irregularity shall be consideto exist where the horizontal dimension of the latforce resisting system in any storey is more t150 percent of that in its adjacent storeyIn-Plane Discontinuity in VerticalElenrentsResistLateral ForceA in-plane offset of the lateral force resistielements greater than the length of those elemeDiscontinuity in CapaciQ WeakStroreyA weak storey is one in which the storey latestrength is less than 80 percent of that in the stoabove, The storey lateral strength is the tostrength of all seismic force resisting elemesharing the storey shear in the considered directi

Table 6 Importance Factors, 1( Clause 6.4.2)

S1 No. Strue tur e ImportanFacto(1) (2) (3)i) Important service and communitybuildings, such as hospitals; schools;

monumental structures; emergencybuildings like telephone exchange, 1.5television stations, radio stations,railway stations, fire station buildings;large community halls like cinemas,assembly halls and subway stations,power stations

ii) AU other buildings 1.0NOTES1 The design engineer may choose values of importanfactor I greater than those mentioned above.2 Buildings not covered in SI No. (i) and (ii) above mbe designed for higher value ofZ, depending on econostrategy considerations like multi-storey buildings hav


23/45

IS 1893 (Part 1 ): 2002

II\ \ i, /\li

VERTICAL COMPONENTS OFSEISMIC RESISTING SYSTEM

- -- .. .FLOOR

iiAl IJ_ I Az+-----------+f

3 ATorsional Irregularity

-r A\ L> O-15-0,20IL-r7L 7 L2AlA23 B Re-entrant CornerFIG. 3 PLAN IRREGU LARITIES Continued


24/45

IS 1893( Part 1 ) :2002MASS RESISTANCE ECCENTRICITY

mmERTICAL COMPONENTS OF SEISMIC RESISTINGSYSTEME OPENING FLOOR3 C Diaphragm Discontinuity

oD

+--SHEARWALL

///////// ///,// ///////BUILDING SECTION

WALLS

3 D Out-of-Plane OffsetsEE3UILDING PLAN

3 E Non-Parallel System


25/45

IS 1893( Part 1 ) :20

EE llii13li----------------------------.------STOREY STIFFNESSFOR THE BUILDINGB

kn kn-l SOFT STOREY WHEN

kn-2 ki< 0.7 kl+l

H

ki+l +ki+2 +ki+s ~k3 OR ki20 Wi_l

OR Wi> 20 Wl+l

4 B Mass IrregularityFIG 4 VERTICALRREGU LARITIES Continued


26/45

S 1893( Part 1 ): 2002

Q jAAIL >0-15 AIL>O-10ALA4 C Vertical Geometric Iregularity when L2>1.5 L,

STOREY STRENGTH(LATERAL)

B.n

Fn.lFn.2

4 D In-Plane Discontinuity in Vertical Elements Resisting 4 E weak Storey when ~ c 0,8 ~ + 1Lateral Force when b > a


27/45

IS 1893( Part 1 ): 200Table 7 Response Reduction Factor l),R, for Building Systems .

( Clause 6.4.2)S1 No. Lateral Load Resisting System R(1)

i)ii)iii)

iv)

v)

vi)vii)

viii)ix)x)xi)

(2)Building Frame SystemsOrdinary RC moment-resisting frame ( OMRF )2)Special RC moment-resisting frame ( SMRF )3)Steel frame with .

a) Concentric bracesb) Eccentric braces

Steel moment resisting frame designed as per SP 6 ( 6 )Building with Shear Walls4~Load bearing masonry wall buildings)

a) Unreinforcedb) Reinforced with horizontal RC bandsc) Reinforced with horizontal RC bands and vertical bars at corners of rooms and

jambs of openingsOrdinary reinforced concrete shear walls@Ductile shear walls7)Buildings with Dual Systemss)Ordinary shear wall with OMRFOrdinary shear wall with SMRFDuctile shear wall with OMRFDuctile shear wall with SMRF

(3)

3.05 .0

4 .05 .05 .0

1.52.53.0

3 .04.0

3 .04 ,04 .55 .0

0 The va]ues of response riduction fact&s are to be used for buildings with lateral load resisting elements, and not Jufor the lateral load resisting elements built in isolation.2 OMRF are those designed and detailedas per IS 456 or Is 800 but not meeting ductile detailing reqllirertlper IS 13920 or SP 6 (6) respectively.34

56ns

SMRF defined in 4.15.2.Buildings with shear walls also include buildings having shear walls and frames, but where:

a) frames are not designed to carry lateral loads, orb) frames are designed to carry lateral loads but do not fulfil the requirements of dual systems.

Reinforcement should be as per IS 4326.Prohibited in zones IV and V.Ductile shear walls are those designed and detailed as per IS 13920.Buildings with dual systems consist of shear walls ( or braced frames ) and moment resisting frames such that:

a) the two systems are designed to resist the total design force in proportion to their lateral stiffness considerinthe interaction of the dual system at all floor levels,; and


28/45

IS 1893( Part 1 ): 2002Table8 Percentage of Imposed Load to beConsidered in Seismic Weight Calculation

(Clause 7.3.1 )Imposed Uniformity Percentage of ImposedDistributed Floor LoadLoads ( kN/ mz )

(1) (2)Upto and including 3.0 25Above 3.0 50

7.5 Design Lateral Force7.5.1 Buildings andportionsthereofshall bedesignedand constructed, to resist the effects of design lateralforce specified in 7.5.3 as aminimum.7.5.2 The design lateral force shall first be computedfor the building as a whole. This design lateral forceshall then be distributed to the various floor levels.The overall design seismic force thus obtained at eachfloor level, shall thenbe distributed to individual lateralload resisting elements depending on the floordiaphragm action.7.5.3 Design Seismic Base ShearThe total design lateral force or design seismic baseshear ( VB)along any principal direction shallbe determined by the following expression:

whereAh =

w.

V~ = AhW

Design horizontal acceleration spectrumvalue as per 6.4.2, using the fundamentalnatural period T,asper 7.6 in the considereddirection of vibration, andSeismic weight ofthe building as per 7.4.2.

7.6 Fundamental Natural Period7.6.1 The approximate fundamental natural periodof vibration ( T, ), in seconds, of a moment-resistingframe building without brick in.fd panels may beestimated by the empirical expression:

T. = 0,075 h07s for RC frame building= 0.085 h075 for steel frame building

7.6.2 The approximate fundamental natural periodof vibration ( T, ), in seconds, of all other buildings,including moment-resisting fimne buildings with brickintil panels, may be estimated by the empiricalexpression:

0.09= m

whereh=d=

Height ofbuilding, inw as defined in7.6.l;andBase dimension ofthebuilding at the plintlevel, in m, along the considered directionof the lateral force.

7.7 Distribution of Design Force7.7.1 Vertical Distribution of Base Shear to DiffermtFloor LeveLrThe design base shear ( V~ ) computed in 7.5.3 shabe distributed along the height of the building as pethe following expression:

W h,zQi=JB lwhere

Qi =Wi =hi =n .

Design lateral force at floor i,Seismic weight of floor i,Height of floor i measured from base, anNumber of storeys in the building is thnumber of levels at which the masses arlocated.

7.7.2 Distribution of Horizontal Design Lateral Forcto Different Lateral Force Resisting Elements7.7.2.1 In case of buildings whose floors are capablof providing rigid horizontal diaphragm action, thtotal shear in any horizontal plane shall be distributeto the various vertieal elements of lateral force resistinsystem, assuming the floors to be infinitely rigid ithe horizontal plane.7.7.2.2 In case of building whose floor diaphragmscan notbe treated as infinitely rigid in their own planthe lateral shear at each floor shall be distributed


29/45

7.8

2 Reinforced concrete monolithic slab-beam floors orthose consisting of prefabricated/precast elements withtopping reinforced screed can be taken a rigid diaphragms.Dynamic Analysis

7.8.1 Dynamic analysis shall bepefiormed to obtainthedesignseismic force, andits distributiontodifferentlevelsalongtheheight ofthebuildingandtothevariouslateral load resisting elements, for the followingbuildings:

a) Regular buildings Those greater than40 m in height in Zones IV and ~ and thosegreater than 90 m in height in Zones II and111.Modelling as per 7.8.4.5 can be used.

b) irregular buildings ( as defined in 7.1 ) Allfiamedbuildingshigherthan12minZonesIVand~andthosegreaterthan40minheightin Zones 11and III.Theanalyticalmo l fordynamicanalysisof buildings

with unusual configuration should be such that itadequatelymodels the types of irregularities presentin the building configuration. Buildings with planirregularities,asdefimedn Table4 ( asper7.1), cannotbemodelledfordynamic analysisbythemethodgivenin 7.8.4.5.NOTE For irregular buildings, lesser than 40 m inheight in Zones 11and III, dynamic anrdysis, even thoughnot mandatory, is recommended.

7.8.2 Dynamic analysis may be performed eitherby the Time History Method or by the ResponseSpectrum Method. However, in either method, thedesign base shear ( VB ) shall be compared with abaseshmr ( J?B) calculated using a fundamental period T,,where T, is as per 7.6. Where t~is less than ~~, allthe response quantities (for example memberforces,displacements, storey forces, storey shears and basereactions) shall bemultiplied by ~~/ V~.7.8.2.1 The value of damping for buildings maybetakenas 2 and 5 percentof the critical, forthepurposesof dynamic analysis of steel and reinforced concretebuildings, respectively.7.8.3 TimeHistory MethodTime history method of analysis, when used, shallbe based on an appropriate ground motion and shallbe performed using accepted principles of dynamics.7.8.4 Response Spectrum MethodResponse spectrum method of analysis shall beperformed using the design spectrum specified in 6.4.2,or by a site-specific design spectrum mentioned

IS 1893( Part 1 ): 2002buildingshallbepetiormedas perestablishedmethodsofmechanicsusing the appropriatemasses and elasticstiffness of the structural system, to obtain naturalperiods(T) andmodeshapes { } ofthose ofitsmodesofvibration that need tobe considered asper 7.8.4.2.7.8.4.2 Modes to be consideredThe number ofmodes tobe used in the analysis shouldbe such that the sum total ofmodal masses of all modesconsidered is at least 90 percent of the total seismicmass and missing mass correction beyond 33percent.If modes with natural frequency beyond33 Hz are tobe considered, modal combination shall be carried outonly for modes upto 33Hz. The effect of higher modesshall be included by considering missing masscorrection following well established procedures.7.8.4.3 Analysis of building subjected to designforcesThe building may be analyzed by accepted principlesofmechanics for the design forces considered as staticforces.7.8.4.4 Modal combinationThe peak response quantities ( for example, memberforces, displacements, storey forces, storey shearsand base reactions ) shall be combined as per CompleteQuadratic Combination ( CQC ) method.I ,,

wherer .pij =Ai =

Lj =

Number of modes being considered,Cross-modal coeffkient,Response quantity in mode i ( includingsign ),Response quantity in mode j ( includingsign ),

8&(l+J3)~15pij = (l+p2)2+452p( l+/.3)2~=

p=0. ,=

Modal damping ratio (in ffaction) asspecified in 7.8.2.1,Frequency ratio = O,/(oi,Circular frequeney in ith mode, and


30/45

IS 1893 ( Part 1 ) : 20{)2a) If the building does not have closely-spaced

modes, then the peak response quantity( k ) due to all modes considered shall beobtained as

k~ = Absolute value of quantity in mode k, andr = Number of modes being consideredb) If the building has a few closely-spacedmodes( see 3.2), then the peak response quantity

( k ) due to these modes shall be obtainedas

where the summation is for the closely-spaced modesonly This peak response quantity due to the closelyspaced modes ( L ) is then combined with those ofthe remaining well-separated modes by the methoddescribed in 7.8.4.4 (a).7.8.4.5 Buildings with regular, or nominally irregyla~{plan configurations may be modelled as a system ofnm.ses lumped at the floor levelswith eachmass havingone degree of freedom, that of lateral displacementin the direction under consideration. In such a case;the following expressions shall hold in the computationof the various quantities :

a) A40dalA4ass The mockdmass (M~)ofmodek is given by

where~ = Acceleration due to gravity,i~ = Mode shape coefficient at floor J inmode k, andPy = Seismic weight of floor i.

b) Modal Participation Factors Themodal participation factor ( P~ ) of mode k isgiven by:

c

d)

e)

f)

Design Lateral Force at Each Floor in EachMode The peak lateral force ( Qi~) at flooi in mode k is given byQ,k= .4k~,~k ,where.4k = Design horizontal acceleration

spectrum value as per 6.4.2 usingthe natural period of vibration ( Tkof mode k.Storey Shear Forcev in Each Mode Thepeak shear force ( P,k) acting in storey i imode k is given by

&j=l+l

Storey Shear Forcetv due to .411 A40devConividered The peak storey shear force( Vi in storey i due to all modes consideredis obtained by combining those due to eachmode in accordarice with 7:8.4.4.Lateral ~orces at Each Storey Due to .41Mode,v Con,videred The design lateralforces, F,,,,,f and F,, at roof and at floor iF,,,,,f = I;,, ,f, andF, * [/; J.:+,

7.9 Torsion.7.9.1 Provision shall be made jn all buildings foincrease in shear forces on.the lateral force resistingelements resulting from thehorizontal torsional momenarising due to eccentricity between the centre of masand centre of rigidity. The design forces calculatedas in 7,8.4.5 are to be applied at the centre of nl~sappropriately displaced so as to cause designeccentricity ( 7.9.2 ) between the displaced centre omassand centre of rigidity.However, negative torsionashear shall be neglected.7.9.2 The design eccentricity, e~ito be used at floo-.i shall be taken as:

,11.5e,, + 0,05 b,

dl = or e,i 0.05 biwhichever of these gives the more severe effectthe shear of any frame where

dl = Static eccentricity at floor i defined as thedistance between centre ofmass and centr


31/45

IS 1893( Part 1 ) :20027.9.3 In case of highly irregular buildings analyzedaccording to 7.8.4.5, additive shears will besuperimposed for a statically applied eccentricity of+ ().()5b, with respect to the centre of rigidity7.10 Buildings with Soft Storey7.10.1 In case buildings with a flexible storey, suchas the ground storey consisting of open spaces forparking that is Stilt buildings, special arrangement needsto be made to increase the lateral strength and stiffnessof the soft/open storey.7.10.2 Dynamic analysis of building is carried outincluding the strength and stiffness effects of infillsand inelastic deformations in the members, particularly,those in the soft storey, and the members designed

direction under consideration, do not lose their verticaload-carrying capacity under the induced momentresulting from storey deformations equal to R timethe storey displacements calculated as per 7.11.1where R is specified in Table 7.

NOTE For instauce, cnnsider a flat-slab buildingwhich lateral Inad resistance is provided by shear wallSince the Isstersdload resistance rfthe slab-column systeis small. these are nften designed nnly for the graviloads, while all the seismic force is resisted by the shewalls. Even thnugh the slabs and columns are not requireto share the lateral forces, these det-orm with restthe structure. under seismic force, The concern is tbunder such detbrmations, the slab-column system shounot lose its vertical Iuad capucity.

7.11.3 Separation Between .4djacent [Jnitsaccordingly, Two adjacent buildings. or two adjacent units of th7.10.3 Alternatively, the following design criteria are same building with separatiolljoint in between shato be adopted after carrying out the earthquake be separated by a distance equal to the amount R timanalysis, neglecting the effect of infill walls in other the sum of the calculated storey displacements as p7.11.1 of each of them, to avoid damaging con~astoreys: when the two units deflect towards each other. Whe

a) the columns and beams of the soft storey are floor levels of two similar adjacent units or buildingto be designed for 2.5 times the storey shears are at the same elevation levels, factor R in thand moments calculated under seismic loads requirement may be replaced by R/2.specified in the other relevant clauses: or. 7.12 Miscellaneous

b) besides the columns designed and detailedfor the calculated storey shears and moments,shear walls placed symmetrically in bothdirections of the building as far away fromthe centre of the building as feasible; to bedesigned exclusively for 1.5 times the lateralstorey shear force calculated as before,

7.11 Deformations7.11.1 Store,v Drift Limitation

7.12.1 FoundationsThe use of foundations vulnerable to significandifferential settlement due to ground shaking shabe avoided for structures in seismic Zones III, IV anV In seismicZones IVand V,individual spread footinor pile caps shall be interconnected with ties( .~ee5.3.4.1 of 1S4326 ) exceptwhen individual spreafootings are directly supported on rock. All ties shabe capable of carrying, in tension and in compressionan axial force equal to .4, /4 times the larger of th

,1

The storey drift in any storey due to the minimum column or pile cap load, in addition to the otherwisespecified design lateral force, with partial load factor computed forces, Here, i4h is as per 6.4.2.of 1,(). shall not exceed O.()()4 times the storey height, 7.12.2 Cantilever ProjectionivFor the purposes of displacement requirements only( see 7.11.1,7.11.2 and 7.11.3 only), it is permissibleto use seismic force obtained from the computedfundamental period (7) of the building without thelower bound limit on design seismic force specifiedin 7.8.2.There shall be no drift limit for single storey buildingwhich has been designed to accommodate storey drift.

7.12.2.1 Wrtica[ projection,rTower, tanks, parapets, smoke stacks ( chimneys)and other vertical cantilever projections attachedbuildings and projecting above the roof, shall bdesigned and checked for stability for five times thdesign horizontal seismic coefficient Ah specifiein 6.4.2. In the analysis of the building, the weighof these projecting elements will be lumped with th


32/45

IS 1893( Part 1 ): 2002in 6.4.5 (that is = 10/3 A~).7.12.2.3 The increased design forces specifiedin 7.12.2.1 and 7.12.2.2 are only for designing theprojecting parts and their connections with the mainstructures. For the design of the main structure,suchincrease need not be considered.7.12.3 Compound WallsCompound walls shall be designed for the designhorizontal coeftlcient Ah with importance factor1= 1.0 specified in 6.4.2.

7.12.4 Connections Between PartsAll partsofthebuilding, exceptbetweenthe separatiosections, shall be tied together to act as integratedsingle unit. All connections between different partssuch as beams to columns and columns to theirfootings, should be made capable of transmittinga force, in all possible directions, of magnitude(Qi/wi) times but not less t&m 0 05 times the weightof the smaller part or the total of dead and imposedload reaction. Frictional resistance shall not be reliedupon for fulfilling these requirements.


33/45

1S 1893 ( Part 1ANNEX A( Foreword68 72

AND SURROUNDINGSHOWING EPICENTRES 8 ,,~ 48o

KILOMETRES co V&, ~ ~p

o

RA?PUR

@ Government of India, Copyright Year 2001.Based upon Survey of India map with the permission of the Surveyor General of India.The responsibil ity for the correctness of internal details rests with the publisher.


34/45


35/45


36/45

As in the Original Standard, this Page is Intentionally Left Blan


37/45

IS 1893( Part 1) : 200ANNEX D

( Forew ord and Clause 3.15 )COMPREHENSIVE INTENSITY SCALE ( MSK 64 )

The scale was discussed generally at the inter-govermnental meeting convenedbyUNESCO inApril1964. Though not finally approved the scale is morecomprehensive and describes the intensity ofearthquake more precisely. The main definitions usedare followings;

a)

b)

c)Grade 1

Grade 2

Grade 3

Tvpe of Structures (Buildings)Type.4 Building in field-stone, rural

structures, unburnt-brickhouses, clay houses.

Tvpe B Ordinary brick buildings,buildings of large block andprefabricated type, half timberedstructures, buildings in naturalhewn stone,

Tvpe C Reinforced buildings, well builtwooden structures,Definition qfQuantitv:Single, few About 5 percentMany About 50 percentMost About 75 percentCla.~~iflcation of Danlage to BuildingsSlight damage

Moderate damage

Hea ydamage

Fine cracks in plaster:fall of small pieces ofplaster.Small cracks in plaster:fall offairly large piecesof plaster: pantiles slipoff cracks in chimneysparts of chimney falldown,Large and deep cracksin plaster: fall ofchimneys,

d)1.

2.

3.

4.

5.

Intensity ScaleNot noticeable The intensity of tvibration is below the limits of sensibilitythe tremor is detected and recordedseismograph only.Sca~e(y noticeable very slight Vibratiis felt only by individual people at resthouses, especially on upper floorsbuildings.Weak, partially observed only Tearthquake is felt indoors by a few peoploutdoors only in favorable circumstanceThe vibration is like that due to the passinof a light truck. Attentive observers notia slight swinging of hanging objectsomewhat more heavily on upper floors.Largelv ob.verved The earthquake is findoors by many people, outdoors by feHere and there people awake, but no onefrightened. The vibration is like that duethe passing of a heavily loaded trucWindows, doors, and dishes rattle. Flooand walls crack. Furniture begins to shakHanging objects swing slightly. Liquidopen vessels are slightly disturbed.standing motor cars the shock is noticeabAwakeningi) The earthquake is felt indoors by aoutdoors by many. Many people awakA few run outdoors. Animals becom

uneasy. Building tremble throughouHanging objects swing consider~blPictures knock against walls or swing oof place. Occasionally pendulum clocstop. Unstable objects overturn or shOpen doors and windows are thrust opand slamback again. Liquids spill in smamounts from well-filled open containe


38/45

IS 1893( Part 1 ) :20026. Frightening

i) Felt by most indoors and outdoors. Manypeople in buildings are frightened andrun outdoors. A few persons loose theirbalance. Domestic animals run out oftheir stalls. In few instances, dishes andglasswaremaybreak, andbooksfall down.Heavy furniture may possibly move andsmall steeple bells may ring.

ii) Damage of Grade 1is sustained in singlebuildings of Type B and in many of TypeA. Damage in few buildings of Type Ais of Grade 2.iii) In few cases, cracks up to widths of

1cm possiblein wet ground inmountainsoccasional landslips: change in flow ofsprings and in level of well water areobserved.7. Darnuge qf huil in v

i)

ii)

iii)

Most people are frightened and runoutdoors. Many find it difllcult to stand.The vibration is noticed by personsdriving motor cars. Large bells ring.In many buildings of Type C damage ofGrade 1 is caused: in many buildings ofType B damage is of Grade 2. Mostbuildings of Type A suffer damage ofGrade 3, few of Grade 4. In singleinstances, landslides of roadway on steepslopes: crack inroads; seams ofpipelinesdamaged; cracks in stone walls.Waves are formed on water, and ismadeturbid by mud stirred up, Water levelsin wells change. and the flow of springschanges. Some times dry springs havetheir flow resorted and existing springsstop flowing. In isolated instances partsof sand and gravelly banks slip off.

8. Destruction of buildingsi) Fright and panic; also persons drivingmotor cars are disturbed, Here and there

branches of trees break off. Even heavyfurniture moves and partly overturns.Hanging lamps are damaged in part.

roads on steep slopes; cracks in grounupto widths of several centimetres. Watin lakes become turbid. New reservoircome into existence. Dry wells refill anexistingwells becomedry. In many casechange in flow and level of waterobserved.

9. General damage of buildingsi)

ii)

iii)

General panic; considerable damagefurniture. Animals run to and froconfusion, and cry.Many buildings of Type C stier damagof Grade 3, and a few of Grade 4. Manbuildings of Type B show a damageGrade 4 and a few of Grade 5. Manbuildings of Type A suffer damageGrade 5. Monuments and columns faConsiderable damage to reservoirunderground pipes partly broken,individual cases, railway lines are beand roadway damaged.On flat land overflow of water, sand anmud is often observed. Ground crackto widths of up to 10 cm, on slopes anriver banks more than 10 cm. Furthemore, a large number of slight cracksground; falls of rock, many land slidand earth flows; large waves in wateDry wells renew their flow and existinwells dry up.

10. General destruction of building~i) Many buildings of Type C suffer damaof Grade 4, and a few of Grade 5. Ma

buildings of Type B show damageGrade 5. Most of Type A havdestruction of Grade 5. Critical damato dykes and dams. Severe damagebridges. Railway lines are bent slightUnderground pipes are bent or brokeRoad paving and asphalt show wave

ii) In ground, cracks up to widths of sevecent.imetres,sometimesup to 1m, Paralto water courses occur broad fissureLoose ground slides from steep slope


39/45

IS 1893( Part 1 ) :200railway lines. Highways become uselessUnderground pipes destroyed.

ii) Ground considerably distorted by broadcracks and fissures, aswell asmovementin horizontal and vertical directions.Numerous landslips and falls of rocks.The intensity of the earthquake requiresto be investigated specifically,

12, Land.~cape changesi) Practically all structures above and below

ground are greatly damageddestroyed.

ii) The surface of the ground is radicalchanged. Considerable ground cracwith extensive vertical and horizontamovements are observed. Falling of roand slumping of river banks over wiareas, lakes are dammed; waterfallappear and rivers are deflected. Tintensity of the earthquake requiresbe investigated specially.

ANNEX E( Foreword)

ZONE FACTORS FOR SOME IMPORTANT TOWNSTownAgraAhmedabadAjmerAllahabadAhnoraAmbalaArnritsarAsansolAurangabadBahraichBangaloreBarauniBareillyBelgaumBhatindaBhilaiBhopalBhubaneswarBlmjBijapurBikanerBokaro

Zone Zone Facto< Z TbwnIIIHIII11IvIVIvIIIHwIIIvIIIIIIIIII1D111vIIIIII111

0.160.160,100.100,240.240.240,160.100,240.100.240.160.160.160.100.100.160.360.160.160.16

ChitradurgaCoimbatoreCuddaloreCuttackDarbhangaDarjeelingDharwadDebra DunDharampuriDelhiDurfypurGangtokGuwahatiGoaGulbargaGayaGorakhpurHyderabadhllphdJabalpurJaipLLrJamshedpur

ZoneIIHIIII111vlvIIINIIIIv111Nv111IIIIINIIv111IIH

Zone Facto

is.1893.1.2002 Criteria for Earthquake Resistant Design

Documents