Is 1893 (part 1)-2002 Indian Standards Criteria For Earthquake Resistant Design Of Structures Part 1 644c34

IS 1893 ( Part 1 ) :2002

Indian Standard CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES PART 1 GENERAL (

PROVISIONS

Ffth

AND BUILDINGS

Revision )

ICS 91.120.25

0 BIS 2002

BUREAU

OF

INDIAN

STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 June 2002

—..

Price Group 12

IS 1893( Part 1 ) :2002

Indian Standard CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES PART 1 GENERAL (

PROVISIONS

AND BUILDINGS

Fijth Revision )

FOREWORD This Indian Standard ( Part 1 ) ( Fifth Revision) was adopted by the Bureau of Indian Standards, afler the draft finalized by the Earthquake Engineering Sectional Committee had been approved by the Civil Engineering Division Council. Himalayan-Nagalushai region, Indo-Gangetilain, Western India, Kutch and Kathiawarregions are geologically unstable parts of the country, and some devastating earthquakes of the world have occurred there. A major part of the peninsular India has also been visited by strong earthquakes, but these were relatively few in number occurring at much larger time intervals at any site, and had considerably lesser intensity. The earth@ake resistant design of structures taking into seismic data from studies of these Indian earthquakes has become very essential, particularly in view of the intense construction activity all over the country. It is to serve this purpose that IS 1893 : 1962 ‘Recommendations for earthquake resistant design of structures’ was published and revised first time in 1966. As a result of additional seismic data collected in India and further knowledge and experience gained since the publication of the first revision of this standard, the sectional committee felt the need to revise the standard again incorporating many changes, such as revision of maps showing seismic zones and epicentres, and adding a more rational approach for design of buildings and sub-structures of bridges. These were covered in the second revision of 1S 1893 brought out in 1970. As a result of the increased use of the standard, considerable amount of suggestions were received for modifying some of the provisions of the standard and, therefore, third revision of the standard was brought out in 1975. The following changes were incorporated in the third revision: a)

The standard incorporated seismic zone factors (previously given as multiplying factors in the second revision ) on a more rational basis.

b)

Importance factors were introduced to for the varying degrees of importance for various structures.

c)

In the clauses for design of multi-storeyed buildings, the coefficient of flexibility was given in the form of a curve with respect to period of buildings.

d)

A more rational formula was used to combine modal shear forces.

e)

New clauses were introduced for determination of hydrodynamic pressures in elevated tanks.

8

Clauses on concrete and masonry dams were modified, taking into their dynamic behavionr during earthquakes. Simplified formulae for design forces were introduced based on results of extensive studies carried out since second revision of the standard was published.

The fourth revision, brought out in 1984, was prepared to modifi some of the provisions of the standard as a result of experience gained with the use of the standard. In this revision, a number of important basic modifications with respect to load factors, field values of N, base shear and modal analysis were introduced. A new concept of performance factor depending on the structural framing system and on the ductility of construction was incorporated. Figure 2 for average acceleration spectra was also modified and a curve for zero percent damping incorporated.

1

IS 1893( Part 1 ) :2002 In the fifth revision, with a view to keep abreast with the rapid development and extensive research that has been carried out in the field of earthquake resistant design of various structures, the committee has decided to cover the provisions for different types of structures in separate parts. Hence, IS 1893 has been split into the following five parts: Part 1 General provisions and buildings Part 2 Liquid retaining tanks — Elevated and ground ed Part 3 Bridges and retaining walls Part 4 Industrial structures including stack like structures Part 5 Dams and embankments Part 1 contains provisions that are general in nature and applicable to all structures. Also, it contains provisions that are specific to buildings only. Unless stated otherwise, the provisions in Parts 2 to 5 shall be read necessarily in conjunction with the general provisions in Part 1. NOTE — Pending finalization of Parts 2 to 5 of IS 1893, provisions of Part 1 will be read along with the relevant clauses of IS 1893 : 1984 for structures other than buildings.

The following are the major and important moditlcations made in the fifth revision: a)

The seismic zone map is revised with only four zones, instead of five. Erstwhile Zone I has been merged to Zone 11. Hence, Zone I does not appear in the new zoning; only Zones II, 111,IV and V do.

b)

The values of seismic zone factors have been changed; these now reflect more realistic values of effective peak ground acceleration considering Maximum Considered Earthquake ( MCE ) and service life of structure in each seismic zone.

c)

Response spectra are now specified for three types of founding strata, namely rock and hard soil, medium soil and soft soil.

d)

Empirical expression for estimating the fundamental natural period Ta of multi-storeyed buildings with regular moment resisting frames has been revised.

e)

This revision adopts the procedure of first calculating the actual force that maybe experienced by the structure during the probable maximum earthquake, if it were to remain elastic. Then, the concept of response reduction due to ductile deformation or frictional energy dissipation in the cracks is brought into the code explicitly, by introducing the ‘response reduction factor’ in place of the earlier performance factor.

f)

A lower bound is specified for the design base shear of buildings, based on empirical estimate of the fimdarnental natural period Ta.

@ The soil-foundation system factor is dropped. Instead, a clause is introduced to restrict the use of foundations vulnerable to differential settlements in severe seismic zones. h)

Torsional eccentricity values have been revised upwards in view of serious darnages observed in buildings with irregular plans.

J)

Modal combination rule in dynamic analysis of buildings has been revised.

k)

Other clauses have been redrafted where necessary for more effective implementation.

It is not intended in this standard to lay down regulation so that no structure shall suffer any damage during earthquake of all magnitudes. It has been endeavored to ensure that, as far as possible, structures are able to respond, without structural darnage to shocks of moderate intensities and without total collapse to shocks of heavy intensities. While this standard is intended for the earthquake resistant design of normal structures, it has to be emphasized that in the case of special structures, such as large and tall dams, long-span bridges, major industrial projects, etc, site-specific detailed investigation should be undertaken, unless otherwise specified in the relevant clauses.

2

IS 1893( Part 1 ): 2002 Though the basis for the design of different types of structures is covered in this standard, it is not implied that detailed dynamic analysis should be made in every case. In highly seismic areas, construction of a type which entails hea~y debris and consequent loss of life and property, such as masonry, particularly mud masonry and rubble masonry, should preferably be avoided. For guidance on precautions to be observed in the construction of buildings, reference maybe made to IS 4326, IS 13827 and IS 13828. Earthquake can cause damage not only on of the shaking which results from them but also due to other chain effects like landslides, floods, fires and disruption to communication. It is, therefore, important to take necessary precautions in the siting, planning and design of structures so that they are safe against such secondary effects also. The Sectional Committee has appreciated that there cannot bean entirely scientific basis for zoning in view of the scanty data available. Though the magnitudes of different earthquakes which have occurred in the past are known to a reasonable degree of accuracy, the intensities of the shocks caused by these earthquakes have so far been mostly estimated by damage surveys and there is little instrumental evidence to corroborate the conclusions arrived at. Maximum intensity at different places can be fixed on a scale only on the basis of the observations made and recorded after the earthquake and thus a zoning map which is based on the maximum intensities arrived at, is likely to lead in some cases to an incorrect conclusion in view of(a) incorrectness in the assessment of intensities, (b) human error in judgment during the damage survey, and (c) variation in quality and design of structures causing variation in type and extent of damage to the structures for the same intensity of shock. The Sectional Committee has therefore, considered that a rational approach to the problem would be to arrive at a zoning map based on known magnitudes and the known epicentres ( see Annex A ) assuming all other conditions as being average and to modifi such an idealized isoseismal map in light of tectonics ( see Annex B ), lithology ( see Annex C ) and the maximum intensities as recorded from damage surveys. The Committee has also reviewed such a map in the light of the past history and future possibilities and also attempted to draw the lines demarcating the different zones so as to be clear of important towns, cities and industrial areas, after making special examination of such cases, as a little modification in the zonal demarcations may mean considerable difference to the economics of a project in that area. Maps shown in Fig. 1 and 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 level of Zone 11. The Killari area has been included in Zone III and necessary modifications made, keeping in view the probabilistic hazard evaluation. The Bellary isolated zone has been removed. The parts of eastern coast areas have shown similar hazard to that of the Killari area, the level of Zone II has been enhanced to Zone III and 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 goes on progressively increasing from southern peninsular portion to the Himalayan main seismic source, the revised seismic zoning map has given status of Zone III to Narmada Tectonic Domain, Mahanandi Graben and Godawari Graben. This is a logical normalization keeping in view the apprehended higher strain rates in these domains on 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 locally at anyplace due to variation in soil conditions. Earthquake response of systems would be affected by different types of foundation system in addition to variation of ground motion due to various types of soils. Considering the effects in a gross manner, the standard gives guidelines for arriving at design seismic coet%cients based on stiffness of base soil. It is important to note that the seismic coefficient, used in the design of any structure, is dependent on nany variable factors and it is an extremely difficult task to determine the exact seismic coefficient in each given case. It is, therefore, necessa~ to indicate broadly the seismic coefficients that could generally be adopted in different parts or zones of the country though, of course, a rigorous analysis considering all the factors involved has to be made in the case of all important projects in order to arrive at a suitable seismic coeftlcients for design. The Sectional Committee responsible for the formulation of this standard has attempted to include a seismic zoning map (see Fig. 1 ) for this purpose. The object of this map is to classifi the area of the country into a number of zones in which one may reasonably expect earthquake shaking of more or less same maximum intensity in future. The Intensity as per Comprehensive Intensity Scale ( MSK64 ) ( see Annex D ) broadly associated with the various zones is VI ( or less ), VII, VIII and IX ( and above ) for Zones II, III, IV and V respectively. The maximum seismic ground acceleration in each zone cannot be presently predicted with 3

IS 1893( Part 1 ) :2002 accuracy either on a deterministic or on a probabilistic basis. The basic zone factors included herein are reasonable estimates of effective peak ground accelerations for the design of various structures covered in this 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 standard devices having detailed experimental data on the performance should be used. The designer must demonstrate by detailed analyses that these devices provide sufficient protection to the buildings and equipment as envisaged in this standard. Performance of locally assembled isolation and energy absorbing devices should be evaluated experimentally before they are used in practice. Design of buildings and equipment using such device should be reviewed by the competent authority. Base isolation systems are found usefhl for short period structures, say less than 0.7s including soil-structure interaction. In the formulation of this standard, due weightage has been given to international coordination among the standards and practices prevailing in different countries in addition to relating it to the practices in the field in this country. Assistance has particularly been derived from the following publications: a)

UBC 1994, Uniform Building Code, International Conference of Building Officials, Whittier, Ckdifomia, U.S.A.1994.

b)

NEHRP 1991, NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings, Part 1: Provisions,ReportNo. FEMA 222, Federal EmergencyManagement Agency,WashingtO% D.C., U.S.A., January 1992.

c)

NEHRP 1991, NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings, Part 2: Commentary, Report No. FEMA 223, Federal Emergency Management Agency, Washington, D. C., U. S.A., January 1992.

d) NZS 4203:1992, Code of Practice for General Structural Design and Design Loadings for Buildings, Standards Association of New Zealand, Wellington, New Zealand, 1992. In the preparation of this standard considerable assistance has been given by the Department of Earthquake Engineering, University of Roorkee; Indian Institute of Technology, Kanpuq IIT Bombay, Mumbai; Geological Survey 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, unless specifically 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 value observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2:1960 ‘Rules for rounding off numerical values ( revised )’. The number of signflcant places retained in the rounded off value should be the same as that of the specified value in this standard.

(Earthquake Engineering Sectional Committee, CED 39 ) 4

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

IS 1893( Part 1 ): 2002

Indian Standard CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES PART 1 GENERAL

PROVISIONS

( Ffth

AND BUILDINGS

Revision ) Title

IS No.

1 SCOPE 1.1 This standard ( Part 1 ) deals with assessment of seismic loads on various structures and earthquake resistant design of buildings. Its basic provisions are applicable to buildings; elevated structures; industrial and stack like structures; bridges; concrete masonry and earth dams; embankments and retaining walls and other structures.

1343:1980

Code of practice for pre-stressed concrete (first revision )

1498:1970

Classification and identification of soils for general engineering purposes (first revision )

1888:1982

Method of load test on soils (second revision

)

1.2 Temporary elements such as scaffolding, temponuy excavations need not be designed for earthquake forces.

1893 (Part4)

1.3 This standard does not deal with the construction features relating to earthquake resistant design in buildings and other structures. For guidance on earthquake resistant construction of buildings, reference may be made to the following Indian Standards:

Criteria for earthquake resistant design of structures: Part 4 Industrial structures including stack like structures

2131:1981

Method of standard penetration test for soils (first revision )

2809:1972

Glossary of and symbols relating to soil engineering ( jirst

IS 4326,1S 13827, IS 13828,IS 13920and IS 13935.

revision )

2 REFERENCES 2.1 The following Indian Standards are necessary adjuncts to this standard: Is No.

456:2000

Code of practice for plain and ( fourth reinforced concrete

4326:1993

Earthquake resistant design and construction of buildings — Code of practice ( second revision )

6403:1981

Code of practice for determination of bearing capacity of shallow foundations (first revision )

13827:1993

Improving earthquake resistance of earthen buildings — Guidelines

13828:1993

Improving earthquake resistance of low strength masonry buildings — Guidelines

13920:1993

Ductile detailing of reinforced concrete structures subjected to seismic forces — Code of practice

13935:1993

Repair and seismic strengthening of buildings — Guidelines

SP 6 ( 6 ) :1972

Handbook for structural engineers: Application of plastic theory in design of steel structures

)

Code of practice for general construction in steel ( second revision )

875

Glossary of relating to soil dynamics (fzrst revision)

Title

revision

800:1984

2810:1979

Code of practice for design loads ( other than earthquake ) for buildings and structures:

(Part l): 1987 Dead loads — Unit weights of building material and storedmaterials ( second revision) (Part 2):1987

Imposed loads ( second revision)

(Part 3):1987

Wind loads ( second revision)

(Part4 ):1987

Snow loads ( second revision)

(Part 5):1987

Special loads and load combinations ( second revision) 7

PrT-’!?

IS 1893( Part

) :2002

3.11 Effective Peak Ground Acceleration ( EPGA )

3 TERMINOLOGY FOR EARTHQUAKE

ENGINEERING

It is O.4 times the 5 percent damped average spectral acceleration between period 0.1 to 0.3 s. This shall be taken as Zero Period Acceleration ( ZPA ).

3.1 For the purpose of this standard, the following definitions shall apply which are applicable generally to all structures.

3.12 Floor Response Spectra

NOTE — For the definitions of pertaining to soil mechanics and soil dynamics references may be made to IS 2809 and IS 2810.

3.2 Closely-Spaced

Floor response spectra is the response spectra for a time history motion of a floor. This floor motion time history is obtained by an analysis of multi-storey building for appropriate material damping values subjected to a specified earthquake motion at the base of structure.

Modes

Closely-spaced modes of a structure are those of its natural modes of vibration whose natural frequencies differ from each other by 10 percent or less of the lower frequency.

3.13 Focus The originating earthquake source of the elastic waves inside the earth which cause shaking of ground due to earthquake.

3.3 Critical Damping The damping beyond which the free vibration motion will not be oscillatory.

3.14 Importance Factor (1) It is a factor used to obtain the design seismic force depending on the functional use of the structure, characterised by hazardous consequences of its failure, its post-earthquake functional need, historic value, or economic importance.

3.4 Damping The effect of internal friction, imperfect elasticity of material, slipping, sliding, etc in reducing the amplitude of vibration and is expressed as a percentage of critical damping. 3.5 Design Acceleration

3.15 Intensity of Earthquake

Spectrum

The intensity of an earthquake at a place is a measure of the strength of shaking during the earthquake, and is indicated by a number according to the modified Mercalli Scale or M. S.K. Scale of seismic intensities (see AnnexD ).

Design acceleration spectrum refers to an average smoothened plot of maximum acceleration as a fimction of frequency or time period of vibration for a specitled damping ratio for earthquake excitations at the base of a single degree of freedom system. 3.6 Design Basis Earthquake

3.16 Liquefaction

( DBE )

Liquefaction is a state in saturated cohesionless soil wherein the effective shear strength is reduced to negligible value for all engineering purpose due to pore pressure caused by vibrations during an earthquake when they approach the total confining pressure. In this condition the soil tends to behave like a fluid mass.

It is the earthquake which can reasonably be expected to occur at least once during the design life of the structure. 3.7 Design Horizontal

Acceleration

Coefficient

(Ah)

3.17 Lithological

It is a horizontal acceleration coefficient that shall be used for design of structures. 3.8 Design Lateral

Features

The nature of the geological formation of the earths crust above bed rock on the basis of such characteristics as colour, structure, mineralogical composition and grain size.

Force

It is the horizontal seismic force prescribed by this standard, that shall be used to design a structure.

3.18 MagnitudeofEarthquake

( Richter% Magnitude)

3.9 Ductility The magnitude of earthquake is a number, which is a measure of energy released in an earthquake. It is defined as logarithm to the base 10 of the maximum trace amplitude, expressed in microns, which the standard short-period torsion seismometer ( with a period of 0.8s, magnification 2800 and damping nemly critical ) would due to the earthquake at an epicentral distance of 100 km.

Ductility of a structure, or its , is the capacity to undergo large inelastic deformations without significant loss of strength or stiffness. 3.10 Epicentre The geographical point on the surface of earth vertically above the focus of the earthquake. 8

IS 1893( Part 1 ) :2002 idealized single degree freedom systems having certain period and damping, during earthquake ground motion. The maximum response is plotted against the undamped natural period and for various damping values, and can be expressed in of maximum absolute acceleration, maximum relative velocity, or maximum relative displacement.

3.19 Maximum Considered Earthquake ( MCE ) The most severe earthquake effects considered by this standard. 3.20 Modal Mass ( lf~ ) Modal mass of a structure subjected to horizontal or vertical, as the case maybe, ground motion is apart of the total seismic mass of the structure that is effective in mode k of vibration. The modal mass for a given mode has a unique value irrespective of scaling of the mode shape. 3.21 Modal Participation

3.28 Seismic Mass It is the seismic weight divided by acceleration due to gravity. 3.29 Seismic Weight (W)

Factor ( Pk)

It is the total dead load plus appropriate amounts of specified imposed load.

Modal participation factor of mode k of vibration is the amount by which mode k contributes to the overall vibration of the structure under horizontal and vertical earthquake ground motions. Since the amplitudes of 95 percent mode shapes can be scaled arbitrarily, the value of this factor depends on the scaling used for mode shapes.

3.30 Structural

Response Factors ( S,/g )

It is a factor denoting the acceleration response spectrum of the structure subjected to earthquake ground vibrations, and depends on natural period of vibration and damping of the structure.

3.22 Modes of Vibration ( see Normal Mode)

3.31 Tectonic Features

3.23 Mode Shape Coefficient ( $i~) When a system is vibrating in normal mode k, at any particular instant of time, the amplitude of mass i expressed as a ratio of the amplitude of one of the masses of the system, is known as mode shape coefficient ( @i~).

The nature of geological formation of the bedrock in the earth’s crust revealing regions characterized by structural features, such as dislocation, distortion, faults, folding, thrusts, volcanoes with their age of formation, which are directly involved in the earth movement or quake resulting in the above consequences.

3.24 Natural Period (T)

3.32 Time History Analysis

Natural period of a structure is its time period of undamped free vibration.

It is an analysis of the dynamic respmse of the structure at each increment of time, when its base is subjected to a specific ground motion time history.

3.24,1 Fundamental

Natural

Period ( T1)

3.33 Zone Factor (Z) It is the first ( longest ) modal time period of vibration.

It is a factor to obtain the design spectrum depending on the perceived maximum seismic risk characterized by Maximum Considered Earthquake ( MCE ) in the zone in which the structure is located. The basic zone fiwtorsincluded in this standard are reasonable estimate of effective peak ground acceleration.

3.24.2 Modal Natural Period ( T~) The modal natural period of mode k is the time period of vibration in mode k. 3.25 Normal Mode

3.34 Zero Period Acceleration ( ZPA )

A system is said to be vibrating in a normal mode when all its masses attain maximum values of displacements and rotations simultaneously, and through equilibrium positions simultaneously.

It is the value of acceleration response spectrum for period below 0.03 s ( frequencies above 33 Hz). -,. 4 TERMINOLOGY FOR EARTHQUAKE ENGINEERING OF BUILDINGS

3.26 Response Reduction Factor (R) It is the factor by which the actual base shear force, that would be generated if the structure were to remain elastic during its response to the Design Basis Earthquake ( DBE ) shaking, shall be reduced to obtain the design lateral force. 3.27 Response

4.1 For the purpose of earthquake resistant design ofbuildings in this standard, the following definitions shall apply. 4.2 Base It is the level at which inertia forces generated in the strnctnre are transferred to the foundation, which then transfers these forces to the ground.

Spectrum

The representation

of the maximum response of 9

IS 1893( Part 1 ) :2002 4.3 Base Dimensions (d)

4.14 Lateral Force Resisting Element

Base dimension of the building along a direction is the dimension at its base, in metre, along that direction.

It is part of the structural system assigned to resist lateral forces.

4.4 Centre of Mass

4.15 Moment-Resisting Frame

The point through which the resultant of the masses of a system acts. This point corresponds to the centre of gravity of masses of system.

It is a frame in which and ts are capable of resisting forces primarily by flexure. 4.15.1 Ordinary

4.5 Centre of Stiffness

Moment-Resisting

Frame

It is a moment-resisting frame not meeting special detailing requirements for ductile behaviour.

The point through which the resultant of the restoring forces of a system acts.

4.15.2 Special Moment-Resisting

Frame

It is the value of eccentricity to be used at floor i in torsion calculations for design.

It is a moment-resisting frame specially detailed to provide ductile behaviour and comply with the requirements given in IS 4326 or IS 13920 or SP6(6).

4.7 Design Seismic Base Shear ( V~)

4.16 Number of Storeys ( n )

It is the total design lateral force at the base of a structure.

Number of storeys of a building isthe number of levels above the base. This excludes the basement storeys, where basement walls are connected with the ground floor deck or fitted between the building columns. But, it includes the basement storeys, when they are not so connected.

4.6 Design Eccentricity

( e~i)

4.8 Diaphragm It is a horizontal, or nearly horizontal system, which transmits lateral forces to the vertical resisting elements, for example, reinforced concrete floors and horizontal bracing systems.

4.17 Principal Axes Principal axes of a building are generally two mutually perpendicular horizontal directions inphmof abuilding along which the geometry of the building is oriented.

4.9 Dual System Buildings with dual system consist of shear walls ( or braced frames ) and moment resisting frames such that: a)

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

b)

The moment resisting frames are designed to independently resist at least 25 percent of the design base shear.

4.18 P-A Effect It is the secondary effect on shears and moments of frame due to action of the vertical loads, interacting with the lateral displacement of building resulting from seismic for~es. 4.19 Shear Wall It is a wall designed to resist lateral forces acting in its own plane. 4.20 Soft Storey

4.10 Height of Floor ( hi )

It is one in which the lateral stiffness is less than 70 percent of that in the storey above or less than 80 percent of the average lateral stiffness of the three storeys above.

It is the difference in levels between the base of the building and that of floor i. 4.11 Height of Structure(k)

4.21 Static Eccentricity

It is the difference in levels, in metres, between its base and its highest level.

( e~l)

It is the distance between centre of mass and centre of rigidity of floor i.

4.12 Horizontal Bracing System It is a horizontal truss system that serves the same function as a diaphragm.

4.22 Storey

4.13 t

4.23 Storey Drift

It is the portion of the column that is common to other , for example, beams, framing into it.

It is the displacement of one level relative to the other level above or below.

It is the space between two adjacent floors.

10

IS 1893( Part 1 ) :2002 4.24 Storey Shear ( ~)

n

Number of storeys

It is the sum of design lateral forces at all levels above the storey under consideration.

N

SPT value for soil

Pk

Modal participation factor of mode k

Q,

Lateral force at floor i

Q~~

Design lateral force at floor i in mode k

r

Number of modes to be considered as per 7.8.4.2

R

Response reduction factor

4.25 Weak Storey It is one in which the storey lateral strength is less than 80 percent of that in the storey above, The storey lateral strength is the total strength of all seismic force resisting elements sharing the storey shear in the considered direction. 5 SYMBOLS

S’a/g Average response acceleration coefficient

The symbols and notations given below apply to the provisions of this standard: .4h

Design horizontal seismic coefficient

A~

Design horizontal acceleration spectrum value for mode “kof vibration

bi

ith Floor plan dimension of the building perpendicular to the direction of force

c

Index for the closely-spaced modes

d

Base dimension of the building, in metres, in the direction in which the seismic force is considered.

DL

Response quantity due to dead load

‘dl

Design eccentricity to be used at floor i calculated as per 7.8.2

e

S1

for rock or soil sites as given by Fig. 2 and Table 3 based on appropriate natural periods and damping of the structure

Static eccentricity at floor i defined as the distance between centre of mass and centre of rigidity

T

Undamped natural period of vibration of the structure (in second )

~

Approximate seconds )

Tk

Undamped natural period of mode k of vibration (in second )

T1

Fundamental natural period of vibration (in second )

VB

Design seismic base shear

pB

Design base shear calculated using the approximate fimdamental period T,

q

Peak storey shear force in storey i due to all modes considered

qk

Shear force in storey i in mode k

fundamental

period ( in

Response quantity due to earthquake load for horizontal shaking along x-direction

v roof Peak storey shear force at the roof due to

ELY

Response quantity due to earthquake load for horizontal shaking along y-direction

w

Seismic weight of the structure

Wi

Seismic weight of floor i

EL,

Response quantity due to earthquake load for vertical shaking along z-direction

z

Zone factor

ELX

all modes considered

Oik

Froof Design lateral forces at the roof due to all

modes considered Fi

Design lateral forces at the floor i due to all modes considered

$?

Acceleration due to gravity

h

Height of structure, in metres

hi

Height measured from the base of the building to floor i

I

Importance factor

IL

Response quantity due to imposed load

h4k

Modal mass of mode k

Mode shape coet%cient at floor i in mode k

11

a

Peak response (for example member forces, displacements, storey forces, storey shears or base reactions ) due to all modes considered

%

Absolute value of maximum response in mode k

kc

Absolute value of maximum response in mode c, where mode c is a closely-spaced mode.

A*

Peak response due to the closely-spaced modes only

IS 1893( Part 1 ) :2002 Pij

oi

for this difference in actual and design lateral loads.

Coefficient used in the Complete Quadratic Combination ( CQC ) method while combining responses of modes i andj

Reinforced and prestressed concrete shall be suitably designed to ensure that premature failure due to shear or bond does not occur, subject to the provisions of IS 456 and IS 1343. Provisions for appropriate ductile detailing of reinforced concrete are given in IS 13920,

Circular frequency in rad/second in the iti mode

6 GENERAL PRINCIPLES AND DESIGN CRITERIA

In steel structures, and their connections should be so proportioned that high ductility is obtain~ tide SP 6 ( Part 6 ), avoiding premature failure due to elastic or inelastic buckling of any type.

6.1 General Principles 6.1.1 Ground

Motion

The characteristics ( intensity, duratio~ etc ) of seismic ground vibrations expected at any location depends upon the magnitude of earthquake, its depth of focus, distance from the epicentre, characteristics of the path through which the seismic waves travel, and the soil strata on which the structure stands. The random earthquake ground motions, which cause the structure to vibrate, can be resolved in any three mutually perpendicular directions. The predominant direction of ground vibration is usually horizontal.

The specified earthquake loads are based upon postelastic energy dissipation in the structure and because of this fact, the provision of this standard for design, detailing and construction shall be satisfied even for structures and for which load combinations that do not contain the earthquake effect indicate larger demands than combinations including earthquake. 6.1.4 Soil-Structure

Interaction

The soil-structure interaction refers to the effects of the ing foundation medium on the motion of structure. The soil-structure interaction may not be considered in the seismic analysis for structures ed on rock or rock-like material.

Earthquake-generated vertical inertia forces are to be considered in design unless checked and proven by specimen calculations to be not significant. Vertical acceleration should be considered in structures with large spans, those in which stability is a criterion for design, or for overall stability analysis of structures. Reduction in gravity force due to vertical component of ground motions can be particularly detrimental in cases of prestressed horizontal and of cantilevered . Hence, special attention should be paid to the effect of vertical component of the ground motion on prestressed or cantilevered beams, girders and slabs.

6.1.5 The design lateral force specified in this standard shall be considered in each of the two orthogonal horizontal directions of the structure. For structures which have lateral force resisting elements in the two orthogonal directions only, the design lateral force shall be considered along one direction at a time, and not in both directions simultaneously. Structures, having lateral force resisting elements (for example frames, shear walls ) in directions other than the two orthogonal directions, shall be analysed considering the load combinations specified in 6.3.2.

6.1.2 The response of a structure to ground vibrations is 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 structures standing on rocks or soils which do not settle, liquefi or slide due to loss of strength during ground vibrations.

Where both horizontal and vertical seismic forces are taken into , load combinations specified in 6.3.3 shall be considered. 6.1.6 Equipment and other systems, which are ed at various floor levels of the structure, will be subjected to motions corresponding to vibration at their points. In important cases, it may be necessary to obtain floor response spectra for design of equipment s. For detail reference be made to IS 1893 (Part 4).

6.1.3 The design approach adopted in this standard is to ensure that structures possess at least a minimum strength to withstand minor earthquakes (
6.1.7 Additions

to Existing Structures

Additions shall be made to existing structures only as follows: a)

12

An addition that is structurally independent from an existing structures shall be designed and constructed in accordance with the seismic requirements for new structures.

IS 1893( Part 1 ): 2002 b)

these shall be combined as per 6.3.1.1 and 6.3.1.2 where the DL, IL and EL stand for the response quantities due to dead load, imposed load and designated earthquake load respectively.

An addition that is not structurally independent from an existing structure shall be designed and constructed such that the entire structure conforms to the seismic force resistance requirements for new structures unless the following three conditions are complied with:

6.3.1.1

3)

for plastic

design

of steel

In the plastic design of steel structures, the following load combinations shall be ed for:

1) The addition shall comply with the requirements for new structures, 2)

Load factors

structures

The addition shall not increase the seismic forces in any structural elements of the existing structure by more than 5 percent unless the capacity of the element subject to the increased force is still in compliance with this standard, and

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 design of reinforced concrete and prestressed concrete structures

The additicn shall not decrease the seismic resistance of any structural element of the existing structure unless reduced resistance is equal to or greater than that required for new structures.

In the limit state design of reinforced and prestressed concrete structures, the following load combinations shall be ed for:

6.1.8 Change in Occupancy

1)

1.5( DL+lL)

When a change of occupancy results in a structure being re-classified to a higher importance factor ( 1 ), the structure shall conform to the seismic requirements for anew structure with the higher importance factor.

2)

1.2( DL+ZL+EL)

3)

1.5( DL+EL)

4)

0.9DL* 1.5EL

6.2 Assumptions

6.3.2 Design Horizontal

The following assumptions shall be made in the earthquake resistant design of structures:

When the lateral load resisting elements are oriented along orthogonal horizontal direction, the structure shall be designed for the effects due to till design earthquake load in one horizontal direction at time.

a)

6.3.2.2 When the lateral load resisting elements are not oriented along the orthogonal horizontal directions, the stmcture shall be designed for the effects due to foil design earthquake load in one horizontal direction plus 30 percent of the design earthquake load in the other direction.

NOTE — However, there are exceptions where resonance-like conditions have been seen to occur between long distance waves and tall structures founded on deep soft soils.

Earthquake is not likely to occur simultaneously with wind or maximum flood or maximum sea waves,

c)

The value of elastic modulus of materials, wherever required, may be taken as for static analysis unless a more definite value is available for use in such condition ( see IS 456, IS 1343 and IS 800 )

Load

6.3.2.1

Earthquake causes impulsive ground motions, which are complex and irregular in character, changing in period and amplitude each lasting for a small duration. Therefore, resonance of the type as visualized under steady-state sinusoidal excitations, will not occur as it would need time to buildup such amplitudes.

b)

Earthquake

NOTE — For instance, the building should be designed for ( + ELx i 0.3 EL.y ) as well as ( * 0.3 ELx * ELy ), where x and y are two orthogonal horizontal directions, EL in 6.3.1.1 and 6.3.1,2 shall be replaced by ( ELx i 0.3 ELy ) or ( ELy i 0.3 .!Lh ).

6.3.3 Design Vertical Earthquake

Load

When effects due to vertical earthquake loads are to be considered, the design vertical force shall be calculated in accordance with 6.4.5. 6.3.4

Combination

for Two or Three Component

6.3 Load Combination and Increase in Permissible Stresses

Motion

6.3.1 Load Combinations

When responses from the three earthquake components are to be considered, the responses due to each component may be combined using the 6.3.4.1

When earthquake forces are considered on a structure, 13

IS 1893( Part 1 ) :2002 Zones III, IV, V and less than 10 in seismic Zone II, the vibration caused by earthquake may cause liquefaction or excessive total and differential settlements. Such sites should preferably be avoided while locating new settlements or important projects. Otherwise, this aspect of the problem needs to be investigated and appropriate methods of compaction or stabilization adopted to achieve suitable N-values as indicated in Note 3 under Table 1. Alternatively, deep pile foundation may be provided and taken to depths well into the layer which is not likely to liquefi. Marine clays and other sensitive clays are also known to lique~ due to collapse of soil structure and will need special treatment according to site condition.

assumption that when the maximum response from one component occurs, the responses from the other two component are 30 percent of their maximum. All possible combinations of the three components ( ELx, ELy and ELz ) including variations in sign ( plus or minus ) shall be considered, Thus, the response due earthquake force (EL ) is the maximum of the following three cases: 1) %ELX*O.3 ELyho.3ELz 2) *ELy*O.3 ELx&O.3 ELz 3)

*ELz*

0.3 ELx&O.3 ELy

where x and y are two orthogonal directions and z is vertical direction.

NOTE — Specialist literature may be referred determining liquefaction potential of a site.

6.3.4.2 As an alternative to the procedure in 6.3.4.1, the response (EL ) due to the combined effect of the three components can be obtained on the basis of ‘square root of the sum of the square ( SRS S )‘ that is EL = ~ (ELx)2+

6.4

Design Spectrum

6.4.1 For the purpose of determining seismic forces, the country is classified into four seismic zones as shown in Fig. 1.

(ELy)z+(ELz)2

6.4.2 The design horizontal seismic coefficient Ah for a structure shall be determined by the following expression:

NOTE — The combination procedure of 6.3.4.1 and 6.3.4.2 apply to the same response quantity (say, moment in a column about its major axis, or storey shear in a frame) due to different components of the ground motion.

.zIsa Ah=—

6.3.4.3 When two component motions ( say one

2Rg

horizontal and one vertical, or only two horizontal) are combined, the equations in 6.3.4.1 and 6.3.4.2 should be modified by del >ting the term representing the response due to the component of motion not being considered. 6.3.5 Increase in Permissible

for

Provided that for any structure with T <0.1 s, the value of A~will not be taken less than Z/2 whatever be the value of I/R where

Stresses

z.

When earthquake forces are considered along with other normal design forces, the permissible stresses in material, in the elastic method of design, maybe increased by one-third. However, for steels having a definite yield stress, the stress be limited to the yield stress; for steels without a definite yield point, the stress will be limited to 80 percent of the ultimate strength or 0.2 percent proof stress, whichever is smaller; and that in prestressed concrete , the tensile stre’ssin the extreme fibers of the concrete may be permitted so as not to exceed two-thirds of the modulus of rupture of concrete.

Zone factor given in Table 2, is for the Maximum Considered Earthquake ( MCE ) and service life of structure in a zone. The factor 2 in the denominator of Z is used so as to reduce the Maximum Considered Earthquake ( MCE ) zone factor to the fktor for Design Basis Earthquake ( DBE ).

z=

Importance factor, depending upon the functional use of the structures, characterised by.hazardous consequences of its failure, post-earthquake functional needs, historical value, or economic importance ( Table 6 ).

6.3.5.2 Increase

R=

Response reduction factor, depending on the perceived seismic damage performance of the structure, characterised by ductile or brittle deformations. However, the ratio (I/R ) shall not be greater than 1.0( Table 7). The values of R for buildings are given in Table 7.

6.3.5.1

Increase impermissible

in allowable

stresses in materials

pressure

in soils

When earthquake forces are included, the allowable bearing pressure in soils shall be increased as per Table 1, depending upon type of foundation of the structure and the type of soil. In soil deposits consisting of submerged loose sands and soils falling under classification SP with standard penetration N-values less than 15 in seismic

S’a/g = Average response acceleration coefficient 14

IS 1893( Part 1 ): 2002 Table 1 Percentage of Permissible Increase in Allowable Bearing Pressure or Resistance of Soils (L’lause 6.3.5.2) Foundation

S1 No.

Type of Soil Mainly Constituting the A r Type I Rock or Hard Soil : Type H Medium S&ls : Well graded gravel and sand All soils with N between 10 gravel mixtures with or and 30, and poorly graded without clay binder, and sands or gravelly sands with clayey sands poorly graded little or no fines ( SP1~) or sand clay mixtures ( GB, with N> 15 CW, SB, SW, and SC )1) having )@ above 30, where N is the standard penetration value

Foundation > Type III Soft Soils: AU soils other than SP’J with N< 10

(1)

(2)

(3)

(4)

(5)

1)

Piles ing through any soil but resting on soil type I

50

50

50

ii)

Piles not covered item i

25

25

iii)

Raft foundations

50

50

50

iv)

Combined isolated RCC footing with tie beams

50

25

25

v)

Isolated RCC footing without tie beams, or unreinforced strip foundations

50

25

—

vi)

Well foundations

50

25

25

under

NOTES 1 The allowable bearing pressure shall be determined in accordance with IS 6403 or IS 1888. 2 If any increase in bearing pressure has already been permitted for forces other than seismic forces, the total increase in allowable bearing pressure when seismic force is also included shall not exceed the limits specified above. 3 Desirable minimum field values of N — If soils of smaller N-values are met, compacting may be adopted to achieve these values or deep pile foundations going to stronger strata should be used. 4 The values of N ( corrected values ) are at the founding level and the allowable bearing pressure shall be determined in accordance with IS 6403 or IS 1888. , Seismic Zone Depth Below Ground N-Values Remark level (in metres ) III, IV and V

11 ( for important structures only )

<5

15

> lo

25

<5 > Ir)

20

15

For values of depths between 5 m and 10 m, linear interpolation is recommended

5 The piles should be designed for lateral loads neglecting lateral resistance of soil layers liable to liquefy. 6 IS 1498 and IS 2131 may also be referred. 7 Isolated R, C.C. footing without tie beams, or unreinforced strip foundation shall not be permitted in soft soils with N<1O. 1) See IS 1498. 2)

See IS 2131.

15

IS-1893 ( Part 1 ) :2002 for rock or soil sites as given by Fig. 2 and Table 3 based on appropriate natural periods and damping of the structure. These curves represent free tleld ground motion.

foundations placed between the ground level and 30 m depth, the design horizontal acceleration spectrum value shall be linearly interpolated between Ah and 0.5 Ah, where Ah is as specified in 6.4.2.

NOTE — For various types of structures, the values of Importance Factor I, Response Reduction Factor R, and damping values are given in the respective parts of this standard. The method ( empirical or otherwise ) to calculate the natural periods of the structure to be adopted for evaluating S,/g is sdso given in the respective parts of this standard.

6.4.5 The design acceleration spectrum for vertical motions, when required, may be taken as two-thirds of the design horizontal acceleration spectrum specitled in 6.4.2. Figure 2 shows the proposed 5 percent spectra for rocky and soils sites and Table 3 gives the multiplying factors for obtaining spectral values for various other clampings.

Table 2 Zone Factor, Z ( Clause 6.4.2) Seismic Zone

II

Seismic Intensity

Low

0.10

z

For rocky, or hard soil sites

Iv

v

Moderate

Severe

Very Severe

0.16

0,24

0.36

111

s, g -1

r

2.50

O.1O

l.00/T

0.40< TS4.00

1+15~

O.OO

2.50

O.1O

I 1.361T

0.55 sT<4.00

s ~ g

=

For soft soil sites

6.4.4 For underground structures and foundations at depths of 30 m or below, the design horizontal acceleration spectrum value shall be taken as half the value obtained from 6.4.2. For structures and

1

0.00< Ts”o.lo

For medium soil sites

6.4.3 Where a number of modes are to be considered for dynamic analysis, the value of Ah as defined in 6.4.2 for each mode shall be determined using the natural period of vibration of that mode.

3.0

=

1+15~

1+15Z

Sa =

T

r

r

I

0.00 S T

2.50

0.10 S TsO.67

1 1.67/T

0.67 ST<4.00

,

,

Type 1 (Rock, or Hard So 2.5 T

.....‘, ‘, ,. ‘! ,, \ ‘.

Type II (Medium Soil) h

/Tv~e II1(Soft Soil)

2.0

1.5

1.0

0.5

—

-----------

--.--.--:.. ........ ---------—

0.0 0.0

0.5

1.0

1“5

2’0

2“5

3“0

3“5

Period(s)

Fm.

2 RESPONSE SPECTRA ~R ROCKANDSOILSITESFOR5 PERC~ DAMPM 16

4“0

IS 1893( Part 1 ): 2002 and 6.3.1.2 where the gravity loads are combined with the earthquake loads [ that is, in load combinations (3) in 6.3.1.1, and (2) in 6.3.1.2 ]. No further reduction in the imposed load will be used as envisaged in IS 875( Part 2 ) for number of storeys above the one under consideration or for large spans of beams or floors.

6.4.6 In case design spectrum is specifically prepared for a structure at a particular project site, the same may be used for design at the discretion of the project authorities

7 BUILDINGS 7.1 Regular and Irregular

Configuration

7.3.4 The proportions of imposed load indicated above for calculating the lateral design forces for earthquakes are applicable to average conditions. Where the probable loads at the time of earthquake are more accurately assessed, the designer may alter the proportions indicated or even replace the entire imposed load proportions by the actual assessed load. In such cases, where the imposed load is not assessed as per 7.3.1 and 7.3.2 only that part of imposed load, which possesses mass, shall be considered. Lateral design force for earthquakes shall not be calculated on contribution of impact effects from imposed loads.

To perform well in an earthquake, a building should possess four main attributes, namely simple and regular cotilguration, and adequate lateral strength, stiffness and ductility. Buildings having simple regolar geomet~ and uniformly distributed mass and stiffness in plan as well as in elevation, suffer much less damage than buildings with irregular configurations. A building shall be considered as irregular for the purposes of this standard, if at least one of the conditions given in Tables 4 and 5 is applicable, 7.2 Importance FactorR

Factor Zand Response Reduction

7.3.5 Other loads apart from those given above ( for example snow and permanent equipment ) shall be considered as appropriate.

The minimum value of importanm factor,1, for ditlerent building systems shall be as given in Table 6. The response reduction factor, R, for different building systems shall be as given in Table 7.

7.4 Seismic Weight 7.4.1 Seismic

7.3 Design Imposed Loads for Earthquakes Force Calculation

Weight of Floors

The seismic weight of each floor is its full dead load plus appropriate amount of imposed load, as specified in 7.3.1 and 7.3.2. While computing the seismic weight of each floor, the weight of columns and walls in any storey shall be equally distributed to the floors above and below the storey.

loading classes as specified in 7.3.1 For various IS 875( Part 2 ), the earthquake force shall be calculatcxl for the full dead load plus the percentage of imposed load as given in Table 8.

7.4.2 Seismic Weight of Building

7.3.2 For calculating the design seismic forces of the structure, the imposed load on roof need not be considered.

The seismic

7.3.3 The percentage of imposed loads given in 7.3.1 and 7.3.2 shall also be used for ‘Whole frame loaded’ condition in the load combinations specified in 6.3. L 1

7.4.3 Any weight ed in between storeys shall be distributed to the floors above and below in inverse proportion to its distance from the floors.

weight

of the whole building

is the sum

of the seismic weights of all the floors.

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

o

2

5

7

10

15

20

25

30

3.20

1,40

1.00

0.90

0.80

0.70

0,60

0.55

0.50

17

IS 1893( Part 1 ) :2002 Table 5 — Concluded

Table 4 Definitions of Irregular Buildings — Plan Irregularities ( Fig. 3 )

Irregularity

S1 No.

( Clause 7.1 )

Type and Description (2)

(1) S1 No.

Irregularity

Type and Description

i)

ii)

(2)

(1)

Mass irregularity shall be considered to exist where the seismic weight of any storey is more than 200 percent of that of its adjacent storeys. The irregularity need not be considered in case of roofs

Torsion Irregularity To be considered when floor diaphragms are rigid in their own plan in relation to the vertical structural elements that resist the lateral forces. Torsional irregularity to be considered to exist when the maximum storey drift, computed with design eccentricity, at one end of the structures transverse to an axis is more than 1.2 times the average of the storey drifts at the two ends of the structure

ii)

Vertical Geometric Irregularity

iii)

Vertical geometric irregularity shall be considered to exist where the horizontal dimension of the lateral force resisting system in any storey is more than 150 percent of that in its adjacent storey

Re-en?rant Corners

iv)

Plan configurations of a structure and its lateral force resisting system contain re-entrant corners, where both projections of the structure beyond the re-entrant corner are greater than 15 percent of its plan dimension in the given direction iii)

Mass Irregulari@

In-Plane Discontinuity in VerticalElenrentsResisttng Lateral Force A in-plane offset of the lateral force resisting elements greater than the length of those elements Discontinuity in CapaciQ — Weak Strorey

v)

A weak storey is one in which the storey lateral strength is less than 80 percent of that in the storey above, The storey lateral strength is the total strength of all seismic force resisting elements sharing the storey shear in the considered direction.

Diaphragm Discontinuity Diaphragms with abrupt discontinuities or variations in stiffness, including those having cut-out or open areas greater than 50 percent of the gross enclosed diaphragm area, or changes in effective diaphragm stiffness of more than 50 percent from one storey to the next

iv)

Table 6 Importance Factors, 1

Out-of-Plane Offsets

( Clause 6.4.2)

Discontinuities in a lateral force resistance path, such as out-of-plane offsets of vertical elements v)

S1 No.

Strue tur e

(1)

(2)

i)

Important service and community buildings, such as hospitals; schools; monumental structures; emergency buildings like telephone exchange, television stations, radio stations, railway stations, fire station buildings; large community halls like cinemas, assembly halls and subway stations, power stations

Non-parallel Systems The vertical elements resisting the lateral force are not parallel to or symmetric about the major orthogonal axes or the lateral force resisting elements

Table 5 Definition of Irregular Buildings — Vertical Irregularities ( Fig. 4 ) ( Clause 7.1 ) S1 No. (1) i)

Irregularity

Type and Description (2)

ii)

a) Stiffness Irregularity — Soft Storey

AU other buildings

Importance Factor (3)

1.5

1.0

NOTES

A soft storey is one in which the lateral stiffness is less than 70 percent of that in the storey above or less than 80 percent of the average lateral stiffness of the three storeys above

1 The design engineer may choose values of importance factor I greater than those mentioned above. 2 Buildings not covered in SI No. (i) and (ii) above may be designed for higher value ofZ, depending on economy, strategy considerations like multi-storey buildings having several residential units.

b) Stiffness Irregularity — Extreme Soft Storey A extreme soft storey is one in which the lateral stiffness is less than 60 percent of that in the storey above or less than 70 percent of the average stiffness of the three storeys above. For example, buildings on STILTS will fall under this category,

3 This does not apply to temporary structures excavations, scaffolding etc of short duration.

18

like

IS 1893 (Part 1 ): 2002

I

\

I \

i,

/ \l

i

.

VERTICAL COMPONENTS OF SEISMIC RESISTING SYSTEM

—-——

--

—..

—.——

FLOOR i i I

Al J_

I

Az

+-----------+f 3 ATorsional Irregularity

-r

I

A\ L> O-15-0,20

IL-r

L

‘7

7

L2

A2

Al

3 B Re-entrant Corner FIG. 3 PLAN IRREGULARITIES — Continued

19

IS 1893( Part 1 ) :2002 MASS

RESISTANCE

ECCENTRICITY

m“m VERTICAL

COMPONENTS OF SYSTEM

E

SEISMIC

RESISTING

OPENING

FLOOR

3 C Diaphragm Discontinuity

+--SHEAR WALL

/////////

///,’//

BUILDING

o D

///////

SECTION

WALLS

3 D Out-of-Plane Offsets

EE3 BUILDING

PLAN

3 E Non-Parallel System FIG. 3 PLAN IRREGULARITIES

20

---------------.------Eli E13 Elii EE!l IS 1893( Part 1 ) :2002

STOREY STIFFNESS FOR THE BUILDING kn #

kn-l

SOFT ki<

kn-2

B

STOREY

OR ki<08

k3

WHEN

0.7 kl+l (

ki+l

+ki+2

+ki+s

3

~ 1

kz k, H //

/

4 A Stiffness Irregularity

SEISMIC WEIGHT Wn w n-l n-2

B

W2 mw

MASS WHEN, OR

4 B Mass Irregularity FIG. 4 VERTICALIRREGULARITIES — Continued

21

IRREGULARITY Wt >20 Wi>

Wi_l

20 Wl+l

IS 1893( Part 1 ): 2002

Q&j A

A

AIL>O-10

AIL >0-15

ALA

b

4 C Vertical Geometric Iregularity

when L2 >1.5 L,

STOREY STRENGTH (LATERAL) Fn

B.

Fn.l

Fn.2

. 4 E weak Storey when ~ c 0,8 ~ + 1

4 D In-Plane Discontinuity in Vertical Elements Resisting Lateral Force when b > a

FIG.4 VEKHCALIRREGULAIUHSS

22

IS 1893( Part 1 ): 2002 Table 7 Response Reduction Factor l), R, for Building Systems

.

( Clause 6.4.2) Lateral

S1 No.

Load Resisting

R

System

(3)

(2)

(1) Building Frame Systems i)

4

Ordinary RC moment-resisting

ii)

Special RC moment-resisting

iii)

Steel frame with

iv)

3.0

frame ( OMRF )2)

5.0

frame ( SMRF )3) .

a) Concentric braces

4.0

b) Eccentric braces

5.0 5.0

Steel moment resisting frame designed as per SP 6 ( 6 ) Building with Shear Walls4~

v)

Load bearing masonry wall buildings) a) Unreinforced

1.5

b) Reinforced with horizontal RC bands

2.5

c) Reinforced with horizontal RC bands and vertical bars at corners of rooms and jambs of openings

3.0

vi)

Ordinary reinforced concrete shear walls@

3.0

vii)

Ductile shear walls7)

4.0”

Buildings with Dual Systemss) viii)

Ordinary shear wall with OMRF

3.0

ix)

Ordinary shear wall with SMRF

4,0

x)

Ductile shear wall with OMRF

4.5

xi)

Ductile shear wall with SMRF

5.0

0 The va]ues of response riduction fact&s are to be used for buildings with lateral load resisting elements, and not Just for 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

reqllirertlellt M

per IS 13920 or SP 6 (6) respectively. b

3)

SMRF defined in 4.15.2.

4) Buildings

with shear walls also include buildings having shear walls and frames, but where:

a) frames are not designed to carry lateral loads, or b) frames are designed to carry lateral loads but do not fulfil the requirements of ‘dual systems’. 5)

Reinforcement

6)

Prohibited in zones IV and V.

n

Ductile shear walls are those designed and detailed as per IS 13920.

s)

Buildings with dual systems consist of shear walls ( or braced frames ) and moment resisting frames such that:

should be as per IS 4326.

a) the two systems are designed to resist the total design force in proportion to their lateral stiffness considering the interaction of the dual system at all floor levels,; and b) the moment resisting frames are designed to independently resist at least 25 percent of the design seismic base shear,

.23

,,

,

IS 1893( Part 1 ): 2002 7.6.2 The approximate fundamental natural period of vibration ( T, ), in seconds, of all other buildings, including moment-resisting fimne buildings with brick intil s, may be estimated by the empirical expression:

Table 8 Percentage of Imposed Load to be Considered in Seismic Weight Calculation 7.3.1 )

(Clause Imposed Uniformity Distributed Floor Loads ( kN/ mz )

Percentage

of Imposed Load

0.09 ‘=

(1)

(2)

Upto and including 3.0

25

Above 3.0

50

m

where h=

Height ofbuilding, inw as defined in7.6.l; and

d=

7.5 Design Lateral Force

7.5.1 Buildings and portionsthereof shall be designed and constructed, to resist the effects of design lateral force specified in 7.5.3 as a minimum.

Base dimension of the building at the plinth level, in m, along the considered direction of the lateral force. .

7.7 Distribution

of Design Force

7.7.1 Vertical Distribution Floor LeveLr

7.5.2 The design lateral force shall first be computed for the building as a whole. This design lateral force shall then be distributed to the various floor levels. The overall design seismic force thus obtained at each floor level, shall thenbe distributed to individual lateral load resisting elements depending on the floor diaphragm action.

of Base Shear to Differmt

The design base shear ( V~ ) computed in 7.5.3 shall be distributed along the height of the building as per the following expression: W h,z

l’

Qi=J’B.

7.5.3 Design Seismic Base Shear where

The total design lateral force or design seismic base shear ( VB) along any principal direction shall be determined by the following expression:

Qi = Design lateral force at floor i, Wi = Seismic weight of floor i,

V~ = AhW

hi = Height of floor i measured from base, and

where n

Ah = Design horizontal acceleration spectrum value as per 6.4.2, using the fundamental natural period T,as per 7.6 in the considered direction of vibration, and

.

Number of storeys in the building is the number of levels at which the masses are located.

7.7.2 Distribution of Horizontal Design Lateral Force to Different Lateral Force Resisting

w.

Seismic weight of the building as per 7.4.2.

7.6.1 The approximate fundamental natural period of vibration ( T, ), in seconds, of a moment-resisting frame building without brick in.fd s may be estimated by the empirical expression:

= 0.085 h075

7.7.2.2 In case of building whose floor diaphragms can not be treated as infinitely rigid in their own plane, the lateral shear at each floor shall be distributed to the vertical elements resisting the lateral forces, considering the in-plane flexibility of the diaphragms.

for RC frame building for steel frame building

where h

=

Elements

7.7.2.1 In case of buildings whose floors are capable of providing rigid horizontal diaphragm action, the total shear in any horizontal plane shall be distributed to the various vertieal elements of lateral force resisting system, assuming the floors to be infinitely rigid in the horizontal plane.

7.6 Fundamental Natural Period

T. = 0,075 h07s

*

Height of building, in m. This excludes the basement storeys, where basement walls are connected with the ground floor deck or fitted between the building columns. But it includes the basement storeys, when they are not so connected.

NOTES 1 A floor diaphragm shaJl be considered to be flexible, if it deforms such that the maximum lateral displacement measured from the chord of the deformed shape at any point of the diaphragm is more than 1.5 times the average displacement of the entire diaphragm. 24

.

IS 1893( Part 1 ): 2002 building shall be petiormed as per established methods of mechanics using the appropriatemasses and elastic stiffness of the structural system, to obtain natural periods (T) and mode shapes {$} of those of its modes of vibration that need to be considered as per 7.8.4.2.

2 Reinforced concrete monolithic slab-beam floors or those consisting of prefabricated/precast elements with topping reinforced screed can be taken a rigid diaphragms.

7.8 Dynamic Analysis 7.8.1 Dynamic analysis shall be pefiormed to obtain the design seismic force, andits distributionto different levels along the height of the building andtothevarious lateral load resisting elements, for the following buildings:

7.8.4.2 Modes to be considered The number of modes to be used in the analysis should be such that the sum total of modal masses of all modes considered is at least 90 percent of the total seismic mass and missing mass correction beyond 33 percent. If modes with natural frequency beyond33 Hz are to be considered, modal combination shall be carried out only for modes upto 33 Hz. The effect of higher modes shall be included by considering missing mass correction following well established procedures.

a) Regular buildings — Those greater than 40 m in height in Zones IV and ~ and those greater than 90 m in height in Zones II and 111. Modelling as per 7.8.4.5 can be used. b) irregular buildings ( as defined in 7.1 ) — Allfiamedbuildingshigherthan12minZones IVand~andthosegreaterthan40minheight in Zones 11and III.

7.8.4.3 Analysis

of building

subjected

to design

forces

The analyticalmo&l fordynamicanalysisof buildings with unusual configuration should be such that it adequately models the types of irregularities present in the building configuration. Buildings with plan irregularities,as defimedin Table4 ( as per 7.1 ), cannot be modelled for dynamic analysis by the method given in 7.8.4.5.

The building may be analyzed by accepted principles of mechanics for the design forces considered as static forces. 7.8.4.4 Modal combination The peak response quantities ( for example, member forces, displacements, storey forces, storey shears and base reactions ) shall be combined as per Complete Quadratic Combination ( CQC ) method.

NOTE — For irregular buildings, lesser than 40 m in height in Zones 11and III, dynamic anrdysis, even though not mandatory, is recommended. 7.8.2

Dynamic

by the

Time

Spectrum

analysis History

Method.

may be performed

Method However,

in either

design base shear ( VB) shall be compared shmr ( J?B) calculated using a fundamental where

either

I

or by the Response method,

,,

the

with abase period T,,

where

T, is as per 7.6. Where t’~is less than ~~, all

the response quantities (for example member forces, displacements, storey forces, storey shears and base reactions) shall be multiplied by ~~ / V~.

r

. Number of modes being considered,

pij

=

Cross-modal coeffkient,

7.8.2.1 The value of damping for buildings maybe takenas 2 and 5 percentof the critical, forthe purposes of dynamic analysis of steel and reinforced concrete buildings, respectively.

Ai

=

Response quantity in mode i ( including sign ),

Lj = Response quantity in mode j ( including sign ),

7.8.3 Time History Method

8&(l+J3)~15

Time history method of analysis, when used, shall be based on an appropriate ground motion and shall be performed using accepted principles of dynamics. ‘7.8.4 Response

pij

(l+p2)2+452p(

7.8.4.1 Free Ebration

Analysis

free vibration

l+/.3)2

~=

Modal damping ratio (in ffaction) as specified in 7.8.2.1,

p=

Frequency ratio = O,/(oi,

0.),=

Circular frequeney in ith mode, and

(l)j=

Circular frequeney injth mode.

Spectrum Method

Response spectrum method of analysis shall be performed using the design spectrum specified in 6.4.2, or by a site-specific design spectrum mentioned in 6.4.6.

Undamped

=

Alternatively, the peak response quantities may be combined as follows:

analysis of the entire 25

.’

IS 1893 ( a)

Part 1 ) : 20{)2

If the building modes,

then

c)

does not have closely-spaced the

( k ) due to all

peak

response

quantity

modes considered shall be

obtained as

Design Lateral Force at Each Floor in Each Mode — The peak lateral force ( Qi~) at floor i in mode k is given by

Q,k = .4k ~,~‘k ‘, where .4k = Design’ horizontal acceleration spectrum value as per 6.4.’2 using the natural period of vibration ( Tk) of mode k.

k~ = Absolute value of quantity in mode k, and r b)

d) Storey Shear Forcev in Each Mode — The peak shear force ( P’,k) acting in storey i in mode k is given by

= Number of modes being considered If the building has a few closely-spaced modes ( see 3.2), then the peak response quantity ( k“ ) due to these modes shall be obtained as

& j=l+l

e)

f)

~orces

at Each

Con,videred

Storey

Due

to .411

—

F,,,,,f = I;,,(,f, and * [/;– J.:+,

F,

7.9 Torsion .!

7.9.1 Provision shall be made jn all buildings for. increase in shear forces on.the lateral force resisting elements resulting from the horizontal torsional moment arising due to eccentricity between the centre of mass and centre of rigidity. The design forces calculated as in 7,8.4.5 are to be applied at the centre of nl~s appropriately displaced so as to cause design eccentricity ( 7.9.2 ) between the displaced centre of, mass and centre of rigidity. However, negative torsional shear shall be neglected.

The mockdmass ( M~) of mode

●

7.9.2 The design eccentricity, e~ito -. be used at floor

where

i shall be taken as:

= Acceleration due to gravity,

1.5e,, + 0,05 b,

$i~ = Mode shape coefficient at floor J in mode k, and

‘dl

=

,1

or

e,i –

0.05 bi

whichever of these gives the more severe effect n the shear of any ’frame where

Py = Seismic weight of floor i. b)

Lateral

The design lateral forces, F,,,,,f and F,, at roof and at floor i :

k is given by

~

Shear Forcetv due to .411 A40dev C’onividered — The peak storey shear force

Mode,v

7.8.4.5 Buildings with regular, or nominally irregyla~{ plan configurations may be modelled as a system of nm.ses lumped at the floor levels with each mass having one degree of freedom, that of lateral displacement in the direction under consideration. In such a case; the following expressions shall hold in the computation of the various quantities : “ A40dalA4ass —

Storey

( Vi) in storey i due to all modes considered is obtained by combining those due to each mode in accordarice with 7:8.4.4.

where the summation is for the closely-spaced modes only This peak response quantity due to the closely spaced modes ( L“ ) is then combined with those of the remaining well-separated modes by the method described in 7.8.4.4 (a).

a)

,

Participation Factors — The modal participation factor ( P~ ) of mode k is given by:

Modal

‘dl =

Static eccentricity at floor i defined as the distance between centre of mass and centre of rigidity, and

b,

Floor plan dimension of floor i, perpendicular to the direction of force.

n

x

‘, @,k

=

NOTE — The

factor 1.5 represents dynamic amplification factor, while the factor 0,05 represents the extent of accidental eccentricity.

,=1

26

.

IS 1893( Part 1 ) :2002 direction under consideration, do not lose their vertical load-carrying capacity under the induced moments resulting from storey deformations equal to R times the storey displacements calculated as per 7.11.1. where R is specified in Table 7.

7.9.3 In case of highly irregular buildings analyzed to 7.8.4”.5, additive shears will be according superimposed for a statically applied eccentricity of + ().()5b, with respect to the centre of rigidity

Buildings with Soft Storey

7.10 7.10.1

In case buildings

as the ground

storey

with a flexible

consisting

parking that is Stilt buildings, to be made to increase of the soft/open

of open spaces

special arrangement

the lateral strength

NOTE — For instauce, cnnsider a flat-slab building in which lateral Inad resistance is provided by shear walls. Since the Isstersdload resistance rfthe slab-column system is small. these are nften designed nnly for the gravity loads, while all the seismic force is resisted by the shear walls. Even thnugh the slabs and columns are not required to share the lateral forces, these det-orm with rest ot’ the structure. under seismic force, The concern is tbtit under such detbrmations, the slab-column system should not lose its vertical Iuad capucity.

storey, such for

needs

and stiffness

storey.

7.10.2 Dynamic analysis of building is carried out including the strength and stiffness effects of infills and inelastic deformations in the , particularly, those in the soft storey, and the designed accordingly,

7.10.3 Alternatively, to be adopted

after

the following carrying

7.11.3 Separation same building

design criteria are

7.11

with separatiollt

in between

shall

times the sum of the calculated storey displacements as per 7.11.1 of each of them, to avoid damaging con~act when the two units deflect towards each other. When floor levels of two similar adjacent units or buildings are at the same elevation levels, factor R in this requirement may be replaced by R/2.

out the earthquake

7.12 Miscellaneous

besides the columns designed and detailed for the calculated storey shears and moments, shear walls placed symmetrically in both directions of the building as far away from the centre of the building as feasible; to be designed exclusively for 1.5 times the lateral storey shear force calculated as before,

7.12.1

Foundations

The use of foundations vulnerable to significant differential settlement due to ground shaking shall be avoided for structures in seismic Zones III, IV and V In seismic Zones IV and V,individual spread footings or pile caps shall be interconnected with ties, ( .~ee5.3.4.1 of 1S4326 ) except when individual spread footings are directly ed on rock. All ties shall be capable of carrying, in tension and in compression, an axial force equal to .4, /4 times the larger of the

Deformations

7.11.1

[Jnits

be separated by a distance equal to the amount R

the columns and beams of the soft storey are to be designed for 2.5 times the storey shears and moments calculated under seismic loads specified in the other relevant clauses: or.

b)

.4djacent

Two adjacent buildings. or two adjacent units of the

analysis, neglecting the effect of infill walls in other storeys: a)

Between

Store,v Drift Limitation

,1

The storey specified

drift design

in any storey lateral

column

due to the minimum

force, with partial

computed

load factor

or pile cap load, in addition forces,

of 1,(). shall not exceed O.()()4 times the storey height,

7.12.2

For the purposes ( see 7.11.1,7.11.2

7.12.2.1 Wrtica[ projection,r

of displacement requirements only and 7.11.3 only), it is permissible

limit on design

seismic

force specified

There shall be no drift limit for single storey building which has been designed 7.11.2 Defer-mation A~enlhers

to accommodate

Conlpatibility

Cantilever

Projectioniv

Tower, tanks, parapets, smoke stacks ( chimneys) and other vertical cantilever projections attached to buildings and projecting above the roof, shall be designed and checked for stability for five times the design horizontal seismic coefficient Ah specified in 6.4.2. In the analysis of the building, the weight of these projecting elements will be lumped with the roof weight.

to use seismic force obtained from the computed fundamental period (7’) of the building without the lower bound in 7.8.2.

to the otherwise

Here, i4h is as per 6.4.2.

storey drift.

of Non-Se isnlic

7.12.2.2

Horizontal

projection

All horizontal projections like cornices and balconies shall be designed and checked for stability for five times the design vertical coefficient specified

For building located in seismic Zones IV and ~ it shall be ensured that the structural components, that are not a part of the seismic force resisting system in the 27

IS 1893( Part 1 ): 2002 in 6.4.5 (that is = 10/3 A~).

7.12.4 Connections

7.12.2.3 The increased design forces specified in 7.12.2.1 and 7.12.2.2 are only for deg the projecting parts and their connections with the main structures. For the design of the main structure,such increase need not be considered.

All partsof the building, exceptbetween the separation sections, shall be tied together to act as integrated single unit. All connections between different parts, such as beams to columns and columns to their footings, should be made capable of transmitting a force, in all possible directions, of magnitude ( Qi/wi) times but not less t&m 0.05 times the weight of the smaller part or the total of dead and imposed load reaction. Frictional resistance shall not be relied upon for fulfilling these requirements.

7.12.3 Compound

Walls

Compound walls shall be designed for the design horizontal coeftlcient Ah with importance factor 1= 1.0 specified in 6.4.2.

Between Parts

.

.

28

1S 1893 ( Part 1 ) :2002

ANNEX A ( Foreword) 68°

72°

AND SURROUNDING

SHOWING 8

EPICENTRES

,,~

‘

48o KILOMETRES

32°

c o

n-o

V&,

~

~’p

n

~

RA?PUR

20

2

o

1

16’

1

12“

8°

@ Government

of India, Copyright

Year 2001.

Based upon Survey of India map with the permission of the Surveyor General of India. The responsibility

for the correctness

of internal details rests with the publisher.

The territorial waters of India extend into the sea to distance of twelve nautical miles measured from the appropriate The istrative

headquarters

of Chandigarh,

Haryana and Punjab are at Chandigarh.

The interstate boundaries between Arunachal Pradesh, Assam and Meghalaya shown on this map are as interpreted North-Eastern Areas (Reorganization) Act, 1971, but have yet to be verified. The external boundaries

base line.

and coastlines of India agree with the Record/Maater 29

Copy certified by Survay of India.

from the

1

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

A..>..

IS 1893( Part 1 ): 2002

ANNEX D (

Foreword

and Clause

3.15 )

COMPREHENSIVE INTENSITY SCALE ( MSK 64 ) d) Intensity

The scale was discussed generally at the intergovermnental meeting convened by UNESCO in April 1964. Though not finally approved the scale is more comprehensive and describes the intensity of earthquake more precisely. The main definitions used are followings; a)

Tvpe of Structures

(Buildings)

Type.4 —

Building in field-stone, rural unburnt-brick structures, houses, clay houses.

Tvpe B —

Ordinary brick buildings, buildings of large block and prefabricated type, half timbered structures, buildings in natural hewn stone,

Tvpe C —

Reinforced buildings, well built wooden structures,

b) Definition

c)

Most

About 75 percent

Cla.~~iflcation

of Danlage to Buildings

Fine cracks in plaster: fall of small pieces of plaster.

Grade 1 Slight damage

Grade 2 Moderate damage

Small cracks in plaster: fall of fairly large pieces of plaster: pantiles slip off cracks in chimneys parts of chimney fall down,

Grade 3 Hea%ydamage

Large and deep cracks in plaster: fall of chimneys,

Grade 4 Destruction

Gaps in walls: parts of buildings may collapse: separate parts of the buildings lose their cohesion: and inner walls collapse,

Sca~e(y noticeable (very slight) — Vibration

3.

Weak, partially observed only — The earthquake is felt indoors by a few people, outdoors only in favorable circumstances. The vibration is like that due to the ing of a light truck. Attentive observers notice a slight swinging of hanging objects. somewhat more heavily on upper floors.

4.

Largelv ob.verved — The earthquake is felt

i)

The earthquake is felt indoors by all, outdoors by many. Many people awake. A few run outdoors. Animals become uneasy. Building tremble throughout. Hanging objects swing consider~bly. Pictures knock against walls or swing out of place. Occasionally pendulum clocks stop. Unstable objects overturn or shift. Open doors and windows are thrust open and slam back again. Liquids spill in small amounts from well-filled open containers. The sensation of vibration is like that due to heavy objects falling inside the buildipgs.

ii) Slight damages in buildings of Type A are possible. iii) Sometimes changes in flow of springs. 33

.

2.

5. Awakening

Total collapse of the buildings.

Grade 5 Total damage

Not noticeable — The intensity of the vibration is below the limits of sensibility: the tremor is detected and recorded by seismograph only.

indoors by many people, outdoors by few. Here and there people awake, but no one is frightened. The vibration is like that due to the ing of a heavily loaded truck. Windows, doors, and dishes rattle. Floors and walls crack. Furniture begins to shake. Hanging objects swing slightly. Liquid in open vessels are slightly disturbed. In standing motor cars the shock is noticeable.

Single, few About 5 percent About 50 percent

1.

is felt only by individual people at rest in houses, especially on upper floors of buildings.

qfQuantitv:

Many

Scale

IS 1893( Part 1 ) :2002 6.

roads on steep slopes; cracks in ground upto widths of several centimetres. Water in lakes become turbid. New reservoirs come into existence. Dry wells refill and existing wells become dry. In many cases, change in flow and level of water is observed.

Frightening

i)

ii)

Felt by most indoors and outdoors. Many people in buildings are frightened and run outdoors. A few persons loose their balance. Domestic animals run out of their stalls. In few instances, dishes and glassware may break, and books fall down. Heavy furniture may possibly move and small steeple bells may ring.

9.

i)

Damage of Grade 1 is sustained in single buildings of Type B and in many of Type A. Damage in few buildings of Type A is of Grade 2.

Darnuge qf’ h uildingv

i)

ii)

Most people are frightened and run outdoors. Many find it difllcult to stand. The vibration is noticed by persons driving motor cars. Large bells ring. In many buildings of Type C damage of Grade 1 is caused: in many buildings of Type B damage is of Grade 2. Most buildings of Type A suffer damage of Grade 3, few of Grade 4. In single instances, landslides of roadway on steep slopes: crack inroads; seams of pipelines damaged; cracks in stone walls.

Destruction

i)

of buildings

General panic; considerable damage to furniture. Animals run to and fro in confusion, and cry.

iii) On flat land overflow of water, sand and mud is often observed. Ground cracks to widths of up to 10 cm, on slopes and river banks more than 10 cm. Further more, a large number of slight cracks in ground; falls of rock, many land slides and earth flows; large waves in water. Dry wells renew their flow and existing wells dry up. 10. General destruction

iii) Waves are formed on water, and is made turbid by mud stirred up, Water levels in wells change. and the flow of springs changes. Some times dry springs have their flow resorted and existing springs stop flowing. In isolated instances parts of sand and gravelly banks slip off. 8.

damage

ii) Many buildings of Type C stier damage of Grade 3, and a few of Grade 4. Many buildings of Type B show a damage of Grade 4 and a few of Grade 5. Many buildings of Type A suffer damage of Grade 5. Monuments and columns fall. Considerable damage to reservoirs; underground pipes partly broken, In individual cases, railway lines are bent and roadway damaged.

iii) In few cases, cracks up to widths of 1cm possible in wet ground in mountains occasional landslips: change in flow of springs and in level of well water are observed. 7.

General

i)

of buildings

Fright and panic; also persons driving motor cars are disturbed, Here and there branches of trees break off. Even heavy furniture moves and partly overturns. Hanging lamps are damaged in part.

of building~

Many buildings of Type C suffer damage of Grade 4, and a few of Grade 5. Many buildings of Type B show damage of Grade 5. Most of Type A have destruction of Grade 5. Critical damage to dykes and dams. Severe damage to bridges. Railway lines are bent slightly. Underground pipes are bent or broken. Road paving and asphalt show waves.

ii) In ground, cracks up to widths of several cent.imetres,sometimesup to 1m, Parallel to water courses occur broad fissures. Loose ground slides from steep slopes. From river banks and steep coasts, considerable landslides are possible. In coastal areas, displacement of sand and mud: change of water level in wells; water from canals, lakes. rivers. etc. thrown on land. New lakes occur.

ii) Most buildings of Type C suffer damage of Grade 2, and few of Grade 3, Most buildings of Type B suffer damage of Grade 3. Most buildings of Type A suffer damage of Grade 4. Occasional breaking seams. Memorials and of pipe monuments move and twist. Tombstones o~.erturn. Stone walls collapse.

11, Destruction i)

iii) Small landslips in hollows and on banked j4

Severe damage even to well built buildings. bridges, water dams and

! IS 1893( Part 1 ) :2002 railway lines. Highways become useless Underground pipes destroyed.

ground are destroyed.

12, Land.~cape changes i)

damaged

or

ii) The surface of the ground is radically changed. Considerable ground cracks with extensive vertical and horizontal movements are observed. Falling of rock and slumping of river banks over wide areas, lakes are dammed; waterfalls appear and rivers are deflected. The intensity of the earthquake requires to be investigated specially.

ii) Ground considerably distorted by broad cracks and fissures, as well as movement in horizontal and vertical directions. Numerous landslips and falls of rocks. The intensity of the earthquake requires to be investigated specifically,

&

greatly

Practically all structures above and below

ANNEX E ( Foreword) ZONE FACTORS FOR SOME IMPORTANT TOWNS Town

Zone

Zone Facto< Z

Tb wn

Zone

Zone Facto< Z

Chitradurga

II

0.10

Coimbatore

HI

0,16

Cuddalore

III

0.16

0.10

Cuttack

111

0.16

Iv

0,24

Darbhanga

v

0.36

Ambala

IV

0.24

Darjeeling

lv

0.24

Arnritsar

Iv

0.24

Dharwad

III

0.16

Asansol

III

0,16

Debra Dun

N

0.24

Aurangabad

H

0.10

Dharampuri

III

0,16

Bahraich

w

0,24

Delhi

Iv

0,24

Bangalore

II

0.10

Durfypur

111

0,16

Barauni

Iv

0.24

Gangtok

N

().24

Bareilly

III

0.16

Guwahati

v

0,36

Belgaum

III

0.16

Goa

111

0.16

Bhatinda

III

0.16

Gulbarga

II

0.10

Bhilai

I1

0.10

Gaya

III

0.16

Bhopal

D

0.10

Gorakhpur

N

0.24

Bhubaneswar

111

0.16

Hyderabad

II

0.10

Blmj

v

0.36

hllphd

v

0.36

Bijapur

III

0.16

Jabalpur

111

0.16

Bikaner

III

0.16

JaipLLr

II

0.10

Bokaro

Agra

III

0.16

Ahmedabad

HI

0.16

Ajmer

II

0,10

Allahabad

11

Ahnora

111

0.16

Jamshedpur

H

0,10

Bulandshahr

Iv

0,24

Jhansi

II

0.10

Burdwan

111

0.16

Jodhpur

II

0.10

Cailcut

HI

0.16

Jorhat

v

0,36

Chandigarh

N

().24

Kakrapara

111

().16

Chcnnai

111

0.16

Kalapakkam

111

0.16

35

IS 1893( Part 1 ) :2002 70wn

Zone

Zone Factor

Z

Town

Zone

Zone Factoc

Kanchipuram

III

0.16

Pondicherry

II

0.10

Kanpur

III

0.16

Pune

III

0.16

Karwar

III

0.16

Raipur

II

0.10

Kohima

v

0.36

Rajkot

III

0.16

Kolkata

III

0.16

Ranchi

II

0.10

Kota

II

0,10

Roorkee

W

0.24

II

0.10

Kurnool

II

0.10

Rourkela

Lucknow

III

0.16

Sadiya

v

0.36

Ludhiana

Iv

0.24

Salem

III

0.16

Madurai

II

0.10

Simla

lv

0.24

II

0.10

III

0.16

Snnagar

v

0.36

Surat

III

0.16

Tarapur

III

0.16

Tezpur

v

0.36

Mandi

v

0.36

Sironj

Mangalore

III

0.16

Solapur

Monghyr

w

0,24

Moradabad

IV

0,24

Mumbai

III

0.16

Mysore

It

0,10

Nagpur

II

0.10

Nagarjunasagar

II

0.10

Nainital

lv

0.24

Nasik

III

0.16

Nellore

III

0.16

Udaipur

Osmanabad

III

0.16

Panjim

III

0.16

Patiala

III

0.16

Patna

lv

0.24

Pilibhit

lv

0,24

36

Thane

III

0.16

Thanjavur

II

0.10

Thiruvananthapuram

III

0.16

Tiruchirappali

II

0.10

Tiruvennamalai

III

0.16

II

0.10

Vadodara

III

0.16

Varanasi

IiI

0.16

Vellore

III

0.16

Viayawada

IN

0.16

Vkhakhapatnam

It

0.10

Z

IS 1893( Part 1 ): 2002

ANNEX (

F

Foreword)

COMMITTEE COMPOS~ON Earthquake Engineering Sectional Committee, CED 39 Representative(s)

Organization

I

In personal capcity ( 72/6 Civil Lines, Roorkee 247667)

DR A. S. AR~A( Chairman )

Bharat Heavy Electricrd Ltd, New Delhi

SHRIN. C. ADDY DR C. KAME.SHWARA RAO ( Alternate 1 ) SHRIA. K. SINGH( Alternate 11 )

Building Materials New Delhi

Technology

SHRIT. N. GUPTA SHRIJ. K. PRASAD( Alternate )

Council,

Central Building Research Institute, Roorkee

SHRIS. K. MHTAL SHRIV. K. GUPTA( Alternate )

Central Public Works Department, New Delhi

SUPERINTENDING ENGINEER(D) EXECUTIVE ENGINEER(D) HI ( Alternate )

Central Water Commission ( ERDD ), New Delhi

DIRECTOR CMDD ( N&W ) DIRECTOR EMBANKMENT ( N&W) ( Alternate)

Central Water and Power Research Station,

SHRI1. D. GUPTA SHRI S. G. CHAPHALAKAR ( Alternate )

D-CAD Technologies

Department

Pune

DR K. G. BHATIA

Pvt Ltd, New Delhi

Delhi College of Engineering,

DR ( SHRIMATI ) P. R. BOSE

Delhi

SHRIP. C. KGTESWAR RAO SHRIS. RAMANLHAM ( Alternate )

of Atomic Energy, Mumbai

Department of Civil Engineering, Roorkee Department of Earthquake Roorkee, Roorkee

Engineer-in-Cbief’s

&

Promotion

University

Engineering,

PROFASHOKJAIN

of Roorkee,

University

DR S.K. THAKKAR DR D.K. PAUL( Alernate I ) DR S. BASU( Alrernate 11 )

of

COL ( DR

) SHRIPAL SHRIY. K. SINGHAL( Alternate )

Branch, Army Headquarters, New Delhi

Engineers India Ltd, New Delhi

DR V. Y. SALPEKAR SHRIR. K. GROVER( Alternate )

Gammon India Limited, Mumbai

SHRIS. A. REDDI SHRIA. K. CHATTERJEE ( Alternate 1 ) SHRIV. N. HAGGADE( Alternate 11 )

Geological

SHRIP. PANDEY SHRIY. F?SHARDA( Alternate )

Survey of India, Lucknow

t Housing Urban and Development

Corporation,

SHRIV. ROY SHRID. P. SINGH( Alternate )

New Delhi

Indian Institute of Technology, Kanpur

DR S. K. JAIN DR C. V. R. MURTY( Alternate )

Indian Institute

DR RAW SINHA DR A. GOYAL( Al?ernate )

of Technology, Mumbai

Indian Meteorological Department,

DR S. N. ,BHAITACHARYA SHRIV. K. MITTAL( AJternate )

New Delhi

I

( Continued on page 38) I

-

37

IS 1893( Part 1 ): 2002 ( Continued from page 37) Representative(s)

Organization Indian Society of Earthquake Technology, Roorkee

SHRIM. K. GUPTA DR D. K. PAUL( Alrernate )

Larsen and Toubro, Chennai

SHRIK. JAYARAMAN SHRIS. KANAPPAN ( Alternate )

Maharashtra Engineering

SHRIR. L. DAMANI SHRIS. V. KUMARASWAMY( Alternate )

Research Centre ( MERI ), Nasik

Ministry of Surface Transport, New Delhi

SHRIN. K. SINHA SHRIR. S. NINAN( Alternate )

National Geophysical Research Institute ( CSIR ), Hyderabad

SHRIS. C. BHATIA SHRIM. RAVIKUMAR( Alternate )

NationaJ Highway Authority of India, New Delhi

SHRIN. K. SINHA SHRIG. SHARAN( Alternate )

National Hydro-Electric

CHIEPENGINEER,CD-HI

Power Corporation Ltd, New Delhi

National Thermal Power Corporation Ltd, New Delhi

SHRIR. S. BAJAI SHRIH. K. RAMKUMAR ( Alternate )

North Eastern Council, Shillong

SHRIL. K. GANJU SHRIA. D. KHARSHING ( Alternate )

Nuclear Power Corporation,

SHRtU. S. P. VERMA

Railway

Mumbai

Board, Ministry of Railways,

School of Planning and Architecture, Structural Engineering

Tandon Consultants

EXECUTIVEDIRECTOR( B&S ) TDIRECTOR( B&S ) CB-1 ( Alternate )

Lucknow

SHRIV. THIRUVENDGADAM

New Delhi

SHRI C. V. VAIDYANATErAN DR B. SWARAMSARMA( Alternate )

Research Centre ( CSIR ), Chennai

DR MAHESHTANDON SHRIVINAYGUPTA( Alternate )

Ltd, New Delhi

SHRI K. V. SUBRA~ANIAN SHRIM. K. S. YOGI( Alternate

Tata Consulting Engineers, Mumbai

)

Wadia Institute of Himalayan Geology, Debra Dun

SHRISURINDERKUMAR

In personal capacity ( E-53, Kapil Whan Faridabad )

SHRIP. L. NARULA

BIS Directorate GeneraJ

SHRt S.K. JAIN, Director & Head ( Civ Engg ) [ Representing Director General ( Ex-officio ) ] Member-Secretary SHRIS. CHATURVEDI t Director ( Civ Engg ), BIS

Earthquake Resistant Construction Subcommittee, CED 39:1 In personal capacity ( 72/6 Civil Lines, Roorkee 247667)

DR A. S. ARYA( Convener)

Building Material Technology Promotion Council, New Delhi

SHRIT. N. GUPTA SHRIJ. K. PRASAD( Alternate )

Central Building Research Institute, Roorkee

SHRIM. P. JAISINGH SHRIV. K. GUPTA( Alternate )

( Continued on page 39)

38

IS 1893( Part 1 ): 2002 ( Continued from page 38) Representative(s)

Organization Central Public Works Department,

Delhi College of Engineering, Department of Earthquake Roorkee, Roorkee Engineer-in-Chief’s

OFWORKS( NDZ ) SUPERINTENDING ENGINEER(D) ( Alternate

New Delhi

SUPERINTENDING SURVEYOR

DR ( SHRIMATI ) P. R. BOSE

Delhi Engineering,

University

Branch, Army Headquarters,

Housing and Urban Development

Corporation,

DR S. K. THAKKAR DR D. K. PAUL( Alternate )

of

EXECUTIVE ENGINEER( DESIGN)

New Delhi

SHRIB. K. CHAKRABORTY SHRID. P. SINGH ( Alternate )

New Delhi

Hindustan Prefab Ltd, New Delhi

SHRIM. KUNDU

Indian Institute of Technology, Mumbai

DR ALOKGOYAL DR RAVISINHA ( Al[ernate )

Indian Institute of Technology,

DR SUDHIRK. JAIN

Kanpur

DR C. V. R. MURTY (

Alternate )

North Eastern Council, Shillong

SHRi D. N. GHOSAI

Public Works Department, Simla

Goverment of Himachat Pradesh,

SHRIV. KAPUR SHRI V. K KAPOOR(

Public Works Department,

Goverment of Jammu & Kashmir

SHRI G. M. SHOUNTHU

Public Works Department,

Goverment of Assam, Guwahati

SHRI SUBRATACHAKRAVARTY

Alternate )

Public Works Department, Government of Gujarat, Gandhi Nagar

SUPERINTENDING ENGINEER( DESIGN )

Research, Design and Standards Organization,

TDIRECTORSTDS (B&S)lCB-I ASSISTANTDIRECTORSTtX ( B&S )/CB-11 ( Alternate)

Structural Engineering

)

Lucknow

Research Centre ( CSIR ), Chennai

SHRf C. V. VAIDYANATHAN SHR1B. StVARAMASARMA (

Tandon Consultants Pvt Ltd, Delhi

DR MAHESH TANDON SHRIVINAYGUPTA(

Alternate )

Alternate )

Maps Subcommittee, CED 39:4 In personal capacity ( E-53 Kapil VihaC Faridabad )

SHRI P. L. NARULA ( Convener ) BRIG K. K. GUPTA( Alternate

DIRECTOR SHRIL D. GUPTA( Alternate)

Centrrd Water and Power Research Station, Pune

Department of Earthquake Roorkee, Roorkee

Engineering,

Indian Meteorological Department,

University

DR S. BASU DR ASHWANI KUMAR( Alternate)

of

DR S. N. BHATTACHARYA SHRI V. K. MHTAL ( Alternate )

New Delhi

Institute of Petroleum Engineering Oil and Natural Gas Commission,

)

Debra Dun

DEPUTY GENERALMANAGER SUPERINTENDING GEOPHYSICIST(

National Geophysical Research Institute ( CSIR ), Hyderabad

SHRIS, C. BHATIA DR B. K. RASTOG]( Alternate )

Survey of India, Debra Dun

SHRIG. M. LAL

39

Alternate )

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