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IS- 1893 | Earthquakes | Normal Mode
IS- 1893
IS 1893-2002 (PART 1) Indian Standaed Criteria for earthquake Resistant Design of Structures JUNE 2002 Bureau of Indian Standards (BIS) Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002
Editorial note: According to the information provided by the national delegate, seismic code has not been changed since 2002. Indian Standard Criteria for Earthquake resisitant design of Structures Part 1 General Provisions and Buildings (Fifth Revision) is included in the World List 2008.
Comments on Building Codes 1. General a. Name of Country: b. Name of Codes:
c. Issued by: d. Enforcement Year:
INDIA Criteria for earthquake Resistant Design of Structures --- in English --- in Original Language Bureau of Indian Standards (BIS) 2002
2. Structural Design Method a. Format: (please check) □√ Working Stress Design : Allowable Stress ≧ Actual Stress □ Ultimate Strength Design: Ultimate Member Strength ≧ Required Member Strength □√ Limit State Design : Ultimate Lateral Strength ≧ Required Lateral Strength □ Other Design Method : (comment) For masonry and steel structure: Working stress method is adopted while for R.C.C. Limit State Design is adopted. b. Material Strength (Concrete and Steel): In Limit State Design for R.C. Structure: Characteristic strength is defined as 95% confidence of yield strength. f ck = f av − 1.64σ . In Working Stress Design of steel structures, the permissible stress is 0.6 times the yield strength which is increased by 33% in case of earthquake loading. In Working Stress Design of masonry Structure: Permissible stress is taken as ¼ of average crushing strength and it is increased by 33% in case of earthquake loading. c. Strength Reduction Factors: For concrete For steel 1.50 1.15
d. Load Factors for Gravity Loadings and Load Combination: 1.5(DL+LL) 1.2(DL+LL ± EL) 1.5(DL ± EL) 0.9 DL ± 1.5EL e. Typical Live Load Values: Office Buildings : Residential Buildings: 2.5 kN/m2 2.0 kN/m2
f. Special Aspects of Structural Design Method Incase of buildings on stilt, the ground storey is designed for 2.5 times the base shear obtained from analysis. In case that your code is performance-based, please describe the fundamental seismic performance requirement. Structures are designed to earthquake shocks of moderate heavy intensities. intensities and without collapse to shocks of
Indian Standard CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES PART 1 GENERAL PROVISIONS AND BUILDINGS (Fifth Revision) FOREWORD This Indian Standard (Part 1) (Fifth Revision) was adopted by the Bureau of Indian Standards, after the draft finalized by the Earthquake Engineering Sectional Committee had been approved by the Civil Engineering Division Council. Himalayan-Nagalushai region, Indo-Gangetic Plain, Western India, Kutch and Kathiawar regions are geologically unstable parts of the country, and sonic 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 earthquake resistant design of structures taking into account 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 I893: 1962 Recommendations for earthquake resistant design of structures was published and revised first time in l966. 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 epicenters, and adding a more rational approach for design of buildings and sub-structures of bridges. These were covered in the second revision of IS 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 (lie 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 account 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 will respect to period of buildings d) c) f) A more rational formula was used to combine modal shear forces. New clauses were introduced for determination of hydrodynamic pressures in elevated tanks. Clauses on concrete and masonry dams were modified, taking into account their dynamic behaviour during earthquakes Simplified formulae for design forces
was prepared to modify some of the provisions of the standard as a result of experience gained with the use of the standard In this revision. the committee has decided to cover the provisions for different types of structures in separate parts. Also. b) The values of seismic zone factors have been changed.Elevated and ground supported 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. 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 :and curve for zero percent damping incorporated In the fifth revision.Pending finalizations of Part 2 to5 of IS 1893. provisions of Part I will be read along with the relevant clause of IS 1893:1984 for structures other than buildings. Then. the concept of response reduction due Id ductile deformation or frictional energy dissipation in the cracks is brought into the code explicitly. 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. Zone I docs not appear in the new zoning. IS 1893 has been split into the following five parts: Part 1 General provisions and buildings Part 2 Liquid retaining tanks . The following are the major and important modifications made in fifth revision: a) The seismic zone map is revised with only four zones. NOTE: . the provisions in Parts 2 to 5 shall be read necessarily in conjunction with (lie general provisions in Part 1. IV and V do. instead of five Erstwhile Zone I has been merged to Zone II. namely rock and hard soil. Hence. The fourth revision. Hence. medium soil and soft soil d) Empirical expression for estimating the fundamental natural period 7 of multistoreyed buildings with regular moment resisting frames has been revised e) This revision adopts the procedure of first calculating the actual force that may be experienced by the structure during the probable maximum earthquake. by introducing the response reduction factor' in place of the earlier performance factor 24-4 . only Zones II. III. 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. it contains provisions that are specific to buildings only Unless stated otherwise. a number of important basic modifications with respect to load factors. if it were to remain elastic. brought out in 1984.were introduced based on results of extensive studies carried out since second revision of the standard was published.
planning and design of structures so that they are safe against such secondary effects also. long-span bridges. is likely to lead in some cases to an incorrect conclusion in view of (a) incorrectness in the assessment of intensities. For guidance on precautions to be observed in the construction I of buildings. particularly mud masonry and rubble masonry. a clause is introduced to restrict the use of foundations vulnerable to differential settlements in severe seismic zones Torsional eccentricity values have been revised upwards in view of serious damages observed in buildings with irregular plans Modal combination rule in dynamic analysis of buildings has been revised Other clauses have been redrafted where necessary for more effective implementation. fires and disruption to communication. Maximum intensity at different places can be fixed on a scale only on the basis of. such as masonry. IS 13827 and IS 13828. 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 modify such an idealized 24-5 . structures are able to respond. (b) human error in judgment during the damage survey.I) g) A lower bound is specified for the design base shear of buildings. The Sectional Committee has appreciated that there cannot be an entirely scientific basis for zoning in view of the scanty data available. The Sectional Committee has therefore. In highly seismic areas. should preferably be avoided. without structural damage to shocks of 'moderate intensities and without total collapse to shocks of heavy intensities. While tins standard is intended for (lie earthquake resistant design of normal structures. such as large and tall dams. based on empirical estimate of the fundamental natural period Ta The soil-foundation system factor is dropped Instead. site-specific detailed investigation should be undertaken. etc. 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. it is not implied I. It is. 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. that detailed dynamic analysis should be made in every case. h) j) k) It is not intended in this standard to lay down regulation so dial no structure shall suffer any damage during earthquake of all magnitudes It has been endeavoured to ensure that. reference maybe made to IS 4326. it has to be emphasized that in the case of special structures. the observations made and recorded after the earthquake and thus a zoning map which is based on the maximum intensities arrived at. important to take necessary precautions in the siting. as far as possible. therefore. floods. major industrial projects. construction of a type I which entails heavy debris and consequent loss of life and property. unless otherwise specified in the relevant clauses Though the basis for the design of different types of structures is covered in this standard. Though the magnitudes of different earthquakes which have occurred in the past are known to a reasonable degree of accuracy. Earthquake can cause damage not only on account of the shaking which results from them but also due to other chain effects like landslides.
Mahanandi Graben and Godawari Graben. It is. The Intensity as per Comprehensive Intensity Scale (MSK. The basic zone factors included herein are j reasonable estimates of effective peak ground accelerations for the design of various structures covered in this standard. III IV and V respectively. 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 coefficients for design. 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. after making special examination of such cases. VII.isoseismal map in light of tectonics (see Annex B). Maps shown in Fig. the revised seismic zoning map has given status of Zone III to Narmada Tectonic Domain. 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 any place due to variation in soil conditions. The parts of eastern coast areas have shown similar hazard to that of the Killari area. The maximum seismic ground acceleration in each zone cannot be presently predicted with accuracy either on a deterministic or on a probabilistic basis. Zone I and II of the contemporary map have been merged and assigned the level of Zone II. necessary to indicate broadly the seismic coefficients that could generally be adopted indifferent parts or zones of the country though. is dependent on many variable factors and it is an extremely difficult task to determine the exact seismic coefficient in each given case. keeping in view the probabilistic hazard evaluation.64) (see Annex D) broadly associated with the various zones is VI (or less). lithology (see Annex C) and the maximum intensities as recorded from damage surveys. 24-6 . therefore. VIII and IX (and above) for Zones II. The Bellary isolated zone has been removed. used in the design of any structure. The Sectional Committee responsible for (he formulation of this standard has attempted to include a seismic zoning map (see Fig. The object of this map is to classify 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. It is important to note that the seismic coefficient. Considering the effects in a gross manner. the level of Zone II has been enhanced to Zone III and connected with Zone III of Godawari Graben area. 1 and Annexes A. the standard gives guidelines for arriving at design seismic coefficients based on stiffness of base soil. 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 Killari area has been included in Zone III and necessary modifications made. Zone factors for some important towns are given in Annex E. of course. 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. as a little modification in the zonal demarcations may mean considerable difference to the economics of a project in that area. 1) for this purpose. B and C are prepared based on information available upto 1993 In the seismic zoning map. cities and industrial areas.
Indian Institute of Technology. In the formulation of this standard. Assistance has particularly been derived from the following publications: a) UBC 1994.C. India Meteorological Department. and several other organizations.A. Kanpur. expressing the result of a test or analysis. c) NEHRP 1991. Code of Practice for General Structural Design and Design Loadings for Buildings. b) NEHRP 1991. shall be rounded off in accordance with IS 2 : 1960 'Rules for rounding off numerical values (revised)'.S. D. For the purpose of deciding whether a particular requirement of this standard is complied with. The designer must demonstrate by detailed analyses that these devices provide sufficient protection to the buildings and equipment as envisaged in this standard. January 1992.C. Geological Survey of India. Whittier. 1992. New Zealand. Part 1: Provisions. Uniform Building Code. Performance of locally assembled isolation and energy absorbing devices should be evaluated experimentally before they are used in practice... Indian Standard CRITERIA FOR EARTHQUAKE RESISTANT 24-7 . Mumbai. NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings. International Conference of Building Officials. say less than 0. The composition of the Committee responsible for (lie formulation of this standard is given in Annex F. Part 2: Commentary. Design of buildings and equipment using such device should be reviewed by the competent authority.S. January 1992.A. Washington. FEMA 223. U. California. Federal Emergency Management Agency. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. d) NZS 4203: 1992. due weight age 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.. Wellington. Washington. the final value observed or calculated. 1IT Bombay. U. Federal Emergency Management Agency.S. Standards Association of New Zealand. NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings. University of Roorkee. 1994. FEMA 222. U. Report No.A.Base isolation and energy absorbing devices may be used for earthquake resistant design. D. Report No.7 s including soil-structure interaction. The units used with the items covered by (lie symbols shall be consistent throughout this standard. In the preparation of this standard considerable assistance has been given by the Department of Earthquake Engineering. Base isolation systems are found useful for short period structures.. unless specifically noted otherwise. Only standard ' devices having detailed experimental data on the performance should be used.
For guidance on earthquake resistant construction of buildings.Code of practice ( second revision ) 6403 : 1981 Code of practice for determination of bearing capacity of shallow 800:1984 Code of practice for general construction in steel (second revision) 875 Code of practice for design loads (other than earthquake) for buildings and structures: (Part 1): 1987 Dead loads . IS 13920 and IS 13935. IS 13827. 1. bridges. industrial and stack like structures.DESIGN OF STRUCTURES PART 1 GENERAL PROVISIONS AND BUILDINGS (Fifth Revision) 1 SCOPE 1.1 The following Indian Standards arc necessary adjuncts to this standard: IS No. the following definitions shall apply which are applicable generally to all structures. 24-8 . IS 13828. concrete masonry and earth dams.2 Temporary elements such as scaffolding. temporary excavations need not be designed for earthquake forces. Its basic provisions are applicable to buildings. 1. 2 REFERENCES 2. elevated structures. Title 1343: 1980 Code of practice for prestressed 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 ) 1893 (Part 4) 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 terms and symbols relating to soil engineering ( first revision ) 2810: 1979 Glossary of terms relating to soil dynamics (first revision) Earthquake resistant design and construction of buildings .1 This standard (Part 1) deals will assessment of seismic loads on various structures and earthquake resistant design of buildings.Unit weights of building material and stored materials (second revision) (Part2): 1987 Imposed loads (second revision) 1987 Wind loads (second re vision) 1987 Snow loads (second revision) (Part3): 1987 Special loads and load combinations (Second revision) foundations (first revision) 13827: 1993 Improving earthquake resistance of earthen buildings . embankments and retaining walls and other structures.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 4326: 1993 3 TERMINOLOGY FOR EARTHQUAKE ENGINEERING 3. reference may be made to the following Indian Standards: IS 4326.3 This standard does not deal with the construction features relating to earthquake resistant design in buildings and other structures.1 For the purpose of this standard.
or economic importance. 3. imperfect elasticity of material. 3. Floor response spectra is the response spectra for a time history motion of a floor.5 Design Acceleration Spectrum Design acceleration spectrum refers to an average smoothened plot of maximum acceleration as a function of frequency or time period of vibration for a specified damping ratio for earthquake excitations at the base of a single degree of freedom system. This shall be taken as Zero Period Acceleration (ZPA). at the base of structure. earth vertically above the focus of the earthquake.16 Liquefaction Liquefaction is a state in saturated cohesionless soil wherein (lie effective shear strength is reduced to negligible value for all engineering purpose due to pore 24-9 . 3.14 Importance Factor (I) It is a factor used to obtain the design seismic force depending on the functional use of the structure.12 Floor Response Spectra vibration motion will not be oscillatory.2 Closely-Spaced 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.4 times the 5 percent damped average spectral acceleration between period 0.K. 3.10 Epicentre soil mechanics and soil dynamics references may be The geographical point on the surface of made to IS 2809 and IS 2810.15 Intensity of Earthquake The intensity of an earthquake at a place is a measure of the strength of shaking during (lie earthquake. slipping. sliding.13 Focus The originating earthquake source of the elastic waves inside the earth which cause shaking of ground due to earthquake.11 Effective Peak Ground Acceleration (EPGA) It is 0. 3.S. etc by an analysis of multi-storey building for in reducing the amplitude of vibration and appropriate material damping values is expressed as a percentage of critical subjected to a specified earthquake motion damping.3 s.NOTE — For the definitions of terms pertaining to 3.7 Design Horizontal Acceleration Coefficient ( Ah ) It is a horizontal acceleration coefficient that shall be used for design of structures. or its members. its It is the earthquake which can reasonably be expected to occur at least once during post-earthquake functional need.4 Damping This floor motion time history is obtained The effect of internal friction.8 Design Lateral Force It is the horizontal seismic force prescribed by this standard. 3.1 to 0. 3. 3. 3.6 Design Basis Earthquake (DBE) hazardous consequences of its failure. that shall be used to design a structure 3. the design life of the structure. characterized by 3. is the capacity to undergo large inelastic deformations without significant loss of strength or stiffness. historic value. and is indicated by a number according to the modified Mercalli Scale or M.3 Critical Damping The damping beyond which the free 3. 3.9 Ductility Ductility of a structure. 3. Scale of seismic intensities (see Annex D).
3.24 Natural Period (T) Natural period of a structure is its time mineralogical composition and grain size. amplitudes of 95 percent mode shapes can be scaled arbitrarily. structure.2 Modal Natural Period (Tk ) base 10 of the maximum trace amplitude.26 Response Reduction Factor (R) (MCE) The most severe earthquake effects It is the factor by which the actual base shear force. The modal mass for a The representation of the maximum given mode has a unique value irrespective response of idealized single degree freedom systems having certain period and damping. magnification 2 800 and A system is said to be vibrating in a normal damping nearly critical) would register due mode when all its masses attain maximum to the earthquake at an epicentral distance values of displacements and rotations simultaneously. of scaling of the mode shape. or maximum earthquake ground motions. Since the relative displacement.17 Lithological Features the system. the value of this factor depends on the scaling used for mode 3. is known as mode shape The nature of the geological formation of coefficient (φ ) .29 Seismic Weight (W) pressure caused by vibrations during an earthquake when they approach the total confining pressure. that would be generated if the considered by this standard.Earthquake Modal mass of a structure subjected to (DBE) shaking shall be reduced to obtain horizontal or vertical. The 3. which the standard time period of vibration in mode k. 3. 24-10 . 3. The modal natural period of mode k is the expressed in microns.19 Maximum Considered Earthquake 3.3. at any particular instant of time. and pass through of 100 km equilibrium positions simultaneously. and can be expressed in contributes to the overall vibration of the terms of maximum absolute acceleration. ground motion is a part of the total seismic mass of the structure that is effective in 3.8s. It is defined as logarithm to the 3. as the case may be. period of undamped free vibration.24.20 Modal Mass ( M k ) response to the Design Basis . 3.22 Modes of Vibration (see Normal It is the seismic weight divided by acceleration due to gravity.28 Seismic Mass shapes.24. ik the earths crust above bed rock on the basis of such characteristics as colour.27 Response Spectrum mode k of vibration.21 Modal Participation Factor ( Pk ) maximum response is plotted against the Modal participation factor of mode k of undamped natural period arid for various vibration is the amount by which mode k damping values. In tins condition (lie soil tends to behave like a fluid mass. the amplitude of mass (expressed as a ratio of the amplitude of one of the masses of 3. short-period torsion seismometer (with a 3. during earthquake ground motion. structure were to remain elastic during its 3. It is the first (longest) modal time period of which is a measure of energy released in an vibration earthquake. the design lateral force.23 Mode Shape Coefficient (φik ) When a system is vibrating in normal mode k. Mode) 3.18 Magnitude of Earthquake 3.1 Fundamental Natural Period (T1 ) (Richter’s Magnitude) The magnitude of earthquake is a number. structure under horizontal and vertical maximum relative velocity.25 Normal Mode period of 0.
This point bed rock in the earth's crust revealing corresponds to the centre of gravity of regions characterized by structural features. 3. for example. masses of system. the designed to independently resist at following definitions shall apply least 25 percent of the design base shear. which arc directly involved in the restoring forces of a system acts. and depends on natural period of vibration and damping of the structure. and OF BUILDINGS 4. 4. or nearly horizontal system.31 Tectonic Features The nature of geological formation of the the masses of a system acts.6 Design Eccentricity (edi ) the above consequences. 3. such as dislocation.34 Zero Period Acceleration (ZPA) walls (or braced frames) and moment It is the value of acceleration response resisting frames such that: spectrum for period below 0. 3. thrusts. along that direction.30 Structural Response Factors ( S a g ) It is a factor denoting the acceleration response spectrum of the structure subjected to earthquake ground vibrations. in torsion calculations for design.8 Diaphragm It is a horizontal.33 Zone Factor (Z) It is a factor (o 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. volcanoes with their age of The point through which the resultant of formation. which transmits lateral forces to the vertical resisting elements.10 Height of Floor (hi ) generated in the structure are transferred to 24-11 . 4. 4. resist the total design lateral force in proportion to their lateral stiffness 4 TERMINOLOGY FOR considering the interaction of the EARTHQUAKE ENGINEERING dual system at all floor levels. which then transfers these forces lo (lie ground 4. the foundation. distortion.4 Centre of Mass The point through which the resultant of 3.32 Time History Analysis It is an analysis of the dynamic response of the structure at each increment of lime.It is the total dead load plus appropriate amounts of specified imposed load. 4. 4. in metre. It is the value of eccentricity to be used at floor. 4. faults. reinforced concrete floors and horizontal bracing systems.3 Base Dimensions (d) Base dimension of the building along a direction is the dimension at its base.1 For the purpose of earthquake resistant b) The moment resisting frames are design of buildings in (his standard.03s a) The two systems are designed to (frequencies above 33 Hz ). when its base is subjected to a specific ground motion lime history.7 Design Seismic Base Shear (VB ) It is the total design lateral force at the base of a structure.5 Centre of Stiffness folding. The basic zone factors included in this standard are reasonable estimate of effective peak ground acceleration.9 Dual System Buildings with dual system consist of shear 3. the earth movement or quake resulting in 4.2 Base It is the level a (which inertia forces 4.
Ah Design horizontal seismic coefficient 4.19 Shear Wall It is a horizontal truss system that serves It is a wall designed to resist lateral forces the same function as a diaphragm. or less than 80 percent of the average lateral stiffness of the three storeys above. It is a frame in which members and joints are capable of resisting forces primarily by 4. 4.20 Soft Storey It is the portion of the column that is It is one in which the lateral stiffness is less common to other members.15. where considered direction. The storey lateral strength is the number of levels above the base. 4. This total strength of all seismic force resisting elements sharing the storey shear in the excludes the basement storeys. behaviour.14 Lateral Force Resisting Element It is part of the structural system assigned 4. basement walls are connected with the 5 SYMBOLS ground floor deck or fitted between the The symbols and notations given below building columns. when they are not so connected. than 70 percent of that in the storey above beams. 4.23 Storey Drift It is a moment-resisting frame not meeting It is the displacement of one level relative special detailing requirements for ductile to the other level above or below.11 Height of Structure (h) It is the difference in levels. 4.18 P − Δ Effect 24-12 . for example.1 Ordinary Moment-Resisting Frame 4. moments of frame members due to action of the vertical loads. from seismic forces. framing into it.16 Number of Storeys (n) Number of storeys of a building is the above.15 Moment-Resisting Frame and centre of rigidity of floor/.22 Storey flexure.2 Special Moment-Resisting Frame 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 SP 6 (6). 4.21 Static Eccentricity (e si ) to resist lateral forces. 4.It is the difference in levels between the It is the secondary effect on shears and base of the building and that of floor i. It is the space between two adjacent floors. in metres. But. lateral displacement of building resulting between its base and its highest level.15. 4. it includes the apply to the provisions of this standard: basement storeys. It is the distance between centre of mass 4.25 Weak Storey It is one in which the storey lateral strength is less than 80 percent of that in the storey 4. interacting with the 4. 4.12 Horizontal Bracing System 4.13 Joint 4.17 Principal Axes Principal axes of a building are generally Ak Design horizontal acceleration spectrum value for mode k of two mutually perpendicular horizontal vibration directions in plan of a building along which the geometry of the building is oriented. acting in its own plane.24 Storey Shear (Vi ) It is the sum of design lateral forces at all levels above the storey under consideration.
where mode c is a closely spaced mode.2 e si Static eccentricity at floor i defined as the distance between centre of mass and centre of rigidity ELx Response quantity due to earthquake load for horizontal shaking along-xdirection EL y Response quantity due to earthquake bi r R Number of modes to be considered as per 7. DL Response quantity due to dead load edi Design eccentricity to be used at floor i calculated as per 7. in metres. * λ Peak response due to the closelyspaced modes only 24-13 . 2 and Table 3 based on appropriate natural periods and damping of the structure T Undamped natural period of vibration of the structure (in second ) Ta Approximate fundamental period ( in seconds ) Tk Undamped natural period of mode k of vibration (in second ) Tl Fundamental natural period of vibration (in second) Design seismic base shear Design base shear calculated using the approximate fundamental period Ta Peak storey shear force in storey i due to all modes considered Shear force in storey i in mode k VB load for horizontal shaking along–ydirection VB EL z Response quantity due to earthquake load for vertical shaking along zdirection V Froof Design lateral forces at the roof due to i all modes considered Fi g h hi Design lateral forces at the floor (due to all modes considered Acceleration due to gravity Height of structure.8. storey shears or base reactions ) due to all modes considered λ k Absolute value of maximum response in mode k λc Absolute value of maximum response in mode c.4.8. storey forces. in the direction in which the seismic force is considered. in metres Height measured from the base of the building to floor i Vik Vroof Peak storey shear force at the roof W Wi Z due to all modes considered Seismic weight of the structure Seismic weight of floor i Zone factor Mode shape coefficient at floor i in mode k I IL Importance factor Response quantity due to imposed load φik λ M k Modal mass of mode k n N Pk Qi Number of storeys SPT value for soil Modal participation factor of mode k Lateral force at floor / Qik Design lateral force at floor i in mode k Peak response (for example member forces.2 Response reduction factor ( S a g ) Average response acceleration coefficient for rock or soil sites as given by Fig.i th 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. displacements.
duration. its depth of focus.1 General Principles that structures withstand a major earthquake (MCE) without collapse Actual 6. The random earthquake design strength. arising from the additional reserve travel.Coefficient used in the complete due to loss of strength during ground Quadratic combination (CQC) vibrations method while. are relied upon to account ground motions.2 The response of a structure to ground detailing and construction shall be satisfied vibration is a function of the nature of even for structures and members for which foundation soil: materials. ductility. size and load combinations that do not contain the mode of construction of structures and the duration and characteristics of ground earthquake effect indicate larger demands motion I Ins standard specifies design than combinations including earthquake forces for structures standing on rocks or 6. and the soil strata on which the strength in structures over and above the structure stands. cantilevered members Hence. special The specified earthquake loads are based attention should be paid to the effect of vertical component of the ground motion upon post-elastic energy dissipation in the on prestressed or cantilevered beams.4 Soil Structure interaction soils which do not settle. mutually perpendicular directions. etc) forces that appear on structures during of seismic ground vibrations expected at earthquakes are much greater than the any location depends upon the magnitude design forces specified in this standard of earthquake. subject to the are lo be considered in design unless provisions-of IS 456 and IS 1343. from. can be resolved in any three lateral loads. or for In steel structures. Combining responses 6. structure and because of this fact. ensure that premature failure due to shear Earthquake-generated vertical inertia forces or bond does not occur. and over path through which the seismic waves strength. members and their overall stability analysis of structures connections should be so proportioned that Reduction in gravity force due to vertical component of ground motions can be high ductility is obtained. liquefy or slide The soil-structure interaction refers to the effects of the supporting foundation ρ ij 24-14 .1. stability is a criterion for design. resist moderate earthquakes (DBE) without 6 GENERAL PRINCIPLES AND significant structural damage though some DESIGN CRITERIA non-structural damage may occur. characteristics of the material behaviour and detailing. 6. Distance However. girders and slabs. and aims 6.3 The design approach adopted in tins standard is to ensure that structures possess of modes i and j ω i Circular frequency in rad/second in at least a minimum strength to withstand minor earthquakes (<DBE). vide SP 6 (Part 6). particularly detrimental in cases of avoiding premature failure due to elastic or prestressed horizontal members and of inelastic buckling of any type. without damage.1. checked and proven In specimen calculations to be not significant Vertical Provisions for appropriate ductile detailing acceleration should be considered in of reinforced concrete members arc given structures with large spans. which cause the structure for this difference in actual and design to vibrate.1. the provision of this standard for design.1. The Reinforced and prestressed concrete predominant direction of ground vibration members shall be suitably designed to is usually horizontal.1 Ground Motion The characteristics (intensity. those in which in IS 13920. arising from inelastic from the epicentre. which occur the ith mode frequently.
5 The design lateral force sped tied in this standard shall lie considered in each of (lie two orthogonal horizontal directions of the structure.3. 6. NOTE — However. Structures. there arc exceptions where resonance-like conditions have been seen to occur between long distance waves and tall structures founded on deep soft soils.2. load combinations specified in 6. 6. shear walls) in directions other than the two orthogonal directions. Therefore. load combinations specified in 6. which are complex and irregular in character.1. 6. changing in period and amplitude each lasting for a small duration. and not in both directions simultaneously. shall be analysed considering tin. The soil-structure interaction may not be considered in the seismic analysis for structures supported on rock or rock-like material. the structure shall conform to the seismic requirements for a new structure with the higher importance factor. which are supported al various floor levels of the structure. 2) 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. 24-15 .6 Equipment and oilier systems. b) 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: 1) The addition shall comply with the requirements for new structures.medium on the motion of structure. resonance of the type as visualised under steady-state sinusoidal excitations.3 shall be considered 6. having lateral force resisting elements (for example frames. will be subjected to motions corresponding to vibration al their support points. it may be necessary to obtain floor response spectra for design of equipment supports For detail reference he made lo IS 1893 (Part 4). the design lateral force shall be considered along one direction at a time. In important cases. will not occur as it would need time to build up such amplitudes.2 Assumptions The following assumptions shall be made in the earthquake resistant design of structures: a) Earthquake causes impulsive ground motions.1.1.7 Additions to Existing Structures Additions shall be made to existing structures only as follows: a) An addition that is structurally independent from an existing structures shall be designed and constructed in accordance with the seismic requirements for new structures. 1. 6.3. For structures which have lateral force resisting elements in the two orthogonal directions only. and 3) The addition 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.8 Change in Occupancy When a change of occupancy results in a structure being re-classified to a higher importance factor (I). Where both horizontal and vertical seismic forces are taken into account.
3.in 6.2.3.2.1.1 and 6.3 Design Vertical Earthquake Load When effects due to vertical earthquake loads are to be considered. these shall be combined as per ELx ± ELy).3 ELz 2) ± ELy ± 0.3. where x andy are two orthogonal 6.1. All possible combinations of the three components (ELx. ELy and ELz) including variations in sign (plus or minus) shall be considered.2 where the terms DL.3 ELx ).1.1. IS 1343 and IS 800) designed for the effects due to full design earthquake load in one horizontal direction at time. 6. the response due earthquake force (EL) is the maximum of the following three cases: 1) ± ELx ± 0.3 Ely ± 0.3.4 Combination for Two or Three accounted for: Component Motion 1) 1.1 Design Horizontal Earthquake and z is vertical direction.7 (DL ± EL) 3) 1.3.1 Load factors for plastic design of steel structures 6.3 a structure. the accordance with 6.3.2 (OL + IL ± EL) 3) l. IL horizontal directions.3 ELx ± 0.3 Load Combination and Increase in design earthquake load in the other Permissible Stresses direction 6.4.1.5.3 ELy ) as well as ( ± 0.1. c) The value of elastic modulus of materials. the design vertical force shall be calculated in In the plastic design of steel structures.3.2 When the lateral load resisting elements are not oriented along the orthogonal horizontal directions.3.7 (DL + IL) 2) 1.5 (DL + !L) 2) l.1 When the lateral load resisting 6.2 As an alternative to the procedure in elements are oriented along orthogonal 6.3. 6.1 Load Combinations NOTE — For instance.2 Partial safety factors for limit state design of reinforced concrete and prestressed concrete structures In the limit state design of reinforced and prestressed concrete structures.3. the following load combinations shall be accounted for: 1) 1. the response (EL) due to the horizontal direction.3.3. the building should be When earthquake forces are considered on designed lor ( i: ELx t 0.3. Thus.3 ELy where x and y are two orthogonal directions 6. imposed load and designated earthquake load respectively.5EL 6.1.2 6.b) Earthquake is not likely to occur simultaneously with wind or maximum flood or maximum sea waves. may be taken as for static analysis unless a more definite value is available for use in such condition (see IS 456.3.5 (DL ± EL) 4) Q.2 shall be replaced by ( ELx t 0.1 When responses from the three earthquake components are to be considered.3 (DL + IL ± EL) 6.1 and 6.3.3. following load combinations shall be 6.4. the responses due to each component may be combined using the assumption that when the maximum response from one component occurs. and EL stand for the response quantities due to dead load.9DL ± l.4. the responses from the other two component are 30 percent of their maximum. wherever required.3 ELz 3) ± ELz ± 0.3 ELx ± 0.4.3 El. the structure shall be combined effect of the three components 24-16 . the structure shall be designed for the effects due to full design earthquake load in one horizontal direction plus 30 percent of the 6.2. /T/. Load 6.y ) or ( ELy + 0.
4.1 Increase in permissible stresses in materials When earthquake forces are considered along with other normal design forces. 6.4. the stress. postearthquake functional needs. 24-17 .4. for steels having a definite yield stress. this aspect of the problem needs moment in a column about its major axis. I = Importance factor. V and less than 10 in seismic Zone II. characterised by. condition.2 apply to the same response quantity (say.3.3 When two component motions (say Note 3 under Table 1. the equations in to depths well into the layer which is not 6. 6.2 The design horizontal seismic coefficient for a structure shall be determined by the following expression: Ah = Z I Sa 2Rg Provided that for any structure with T ≤ 0. Such sites should preferably be avoided while locating new NOTE — The combination procedure of 6. depending upon type of foundation of the structure and the type of soil.2 percent proof stress.3. the vibration caused by earthquake may of the sum of the square (SRSS)’ that is cause liquefaction or excessive total and EL = ( ELx) 2 f + ( ELy ) 2 + ( ELz ) 2 differential settlements. and that in prestressed concrete members.1 and settlements or important projects. the tensile stress in the extreme fibers of the concrete may be permitted so as not to exceed twothirds of the modulus of rupture of concrete. the value of Ah will not be taken less than Z/2 whatever be the value of where Z = Zone factor given in Table 2.1 s. whichever is smaller. for steels without a definite yield point. depending upon the functional use of the structures.can be obtained on the basis of' square root IV. the stress will be limited to 80 percent of the ultimate strength or 0. 6.4. However.3.3.5. 6. or storey to be investigated and appropriate methods shear in a frame) due to different components of the of compaction or stabilization adopted to ground motion. may be increased by one-third.5.1 For the purpose of determining seismic forces.3. The factor 2 in the denominator of Z is used so as to reduce the Maximum Considered Earthquake (MCE) zone factor to the factor for Design Basis Earthquake (DBE). the country is classified into four seismic zones as shown in Fig. the permissible stresses in material. the stress) limited to the yield stress.3. Otherwise. Alternatively. the allowable bearing pressure in soils shall be increased as per Table 1. 6. or only two pile foundation may be provided and taken horizontal) are combined. NOTE — Specialist literature may be referred for determining liquefaction potential of a site.4. achieve suitable N-values as indicated in 6.4.2 Increase in allowable pressure in soils When earthquake forces are included. In soil deposits consisting of submerged loose sands and soils falling under classification SP with standard penetration N-values less than 15 in seismic Zones III.2 should be modified by likely to liquefy.3.4. deep one horizontal and one vertical.4 Design Spectrum 6.3. hazardous consequences of its failure. is for the Maximum Considered Earthquake (MCE) and service life of structure in a zone. 1. in the elastic method of design. Marine clays and other deleting the term representing the response sensitive clays are also known to liquefy due to collapse of soil structure and will due to the component of motion not being need special treatment according to site considered.5 Increase in Permissible Stresses 6.1 and 6.
Foundation Type of Soil Mainly constituting the Foundation Type I Rock or Hard Soil: Well graded gravel and sand gravel mixtures with or without clay binder. 24-18 . where N is the standard penetration value Type II Medium Soils: All soils with N between 10 and 30. R = Response reduction factor. SW. No.0 (Table 7). or economic importance (Table 6). characterised by ductile or brittle deformations. SB. depending on the perceived seismic damage ( S a performance of the structure. 3 Desirable minimum field values of N . 2.If soils of smaller N-values are met.historical value. the total increase in allowable bearing pressure when seismic force is also included shall not exceed the limits specified above. The allowable bearing pressure shall be determined in accordance with IS 6403 or IS 1888.5.3. and clayey sands poorly graded or sand clay mixtures (GB. or unreinforced strip foundation Well foundation (3) 50 (4) 50 (5) 50 50 50 25 50 25 25 50 25 50 25 - 50 25 25 NOTES 1. CW. and SC)1 having N2 above 30. g ) = Average response acceleration coefficient Table 1 Percentage of Permissible Increase in Allowable Bearing Pressure or Resistance of Soils (Clause 6. However. 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) arc at the founding level and the allowable bearing pressure shall be determined in accordance with IS 6403 or IS 1888. and poorly graded sands or gravelly sands or gravelly sands with little or no fines (SP1) with N>15 Type III Soils: All soils other than (SP1) with N>10 (1) i) ii) iii) iv) v) vi) (2) Piles passing through any soil but resting on soil type I Piles not covered under item: Raft foundations Combined isolated RCC footing with tie beams Isolated RCC footing without tie beams. If any increase in bearing pressure has already been permitted for forces other than seismic forces.2) SI. The values of R for buildings are given in Table 7. the ratio (I/R) shall not be greater than 1.
40 ≤ T ≤ 4.10 0. or hard soil sites Zone ⎧1 + 15 T 0.16 0.00 ≤ T ≤ 0. spectra for rocky and soils sites and Table 3 gives the multiplying factors for obtaining Table 2 Zone Factor. where Ah is as specified in 6.Seismic Zone level (in metres) III.10 0.10 ≤ T ≤ 0. Response Reduction Factor vertical motions.67 / T obtained from 6.4.10 Seismic Low Moderate Severe Very Sa ⎪ = ⎨ 2.5 The design acceleration spectrum for of Importance Factor /.2.4.67 ≤ T ≤ 4. when required.67 0. linear interpolation is recommended The piles should be designed for lateral loads neglecting lateral resistance of soil layers liable to liquefy. For structures and foundations placed between the ground 0.4.2 for each mode = ⎨ 2.C.10 0.2.5 A h h curves represent free field ground motion.2) Seismic II III IV V For rocky. structure to be adopted for evaluating is ( S a g ) also Figure 2 shows the proposed 5 percent given in the respective parts of this standard.50 g ⎪ value shall be taken as half the value ⎩1.3 Where a number of modes are to be For medium soil sites considered for dynamic analysis.00 24-19 . (Clause 6.55 ≤ T ≤ 4.2.55 0.24 0. and damping values are given in the respective parts of this standard.4. Z spectral values for various other dampings. or unreinforced strip foundation shall not be permitted in soft soils with N<10.36 / T of vibration of that mode. IV and V II (for important structures only) 5 6 7 1) 2) Depth below Ground ≤ 5 ≥ 10 ≤ 5 ≥ 10 N-Values Remark 15 25 15 25 For values of depths between 5 m and 10 m. Isolated R.40 Intensity Severe g ⎪ Z 0.00 6.4 For underground structures and For soft soil sites foundations at depths of 30 m or below. The method (empirical or taken as two-thirds of the design horizontal otherwise). to calculate the natural periods of the acceleration spectrum specified in 6. 6.00 ≤ T ≤ 0.50 g ⎪ shall be determined using the natural period ⎩1. may be R. the design horizontal Table 3 based on appropriate natural acceleration spectrum value shall be periods and damping of the structure.50 0.4.10 ≤ T ≤ 0. See IS 1498 See IS 2131 for rock or soil sites as given by Fig.10 ≤ T ≤ 0. NOTE — For various types of structures.C. IS 1498 and IS 2131 may also be referred.00 0. footing without tic beams.00 ≤ T ≤ 0. These linearly interpolated between A and 0. the ⎧1 + 15 T Sa ⎪ design horizontal acceleration spectrum = ⎨ 2.36 ⎩1. the values 6.4. the value ⎧1 + 15 T Sa ⎪ of Ah as defined in 6. 2 and level and 30 m depth.00 / T 0.4.4.
1 For various loading classes as specified in IS 875 (Part 2). 2 Response Spectra For Rock and Soil Sites For 5 Percent Damping 6. A building shall be considered as irregular for the purposes of this standard. namely simple and regular configuration. The response reduction factor.4 The proportions of imposed load indicated above for calculating the lateral design forces for earthquakes are applicable to average conditions.3. the same may be used for design at the discretion of the project' authorities 7 BUILDINGS 7.6 In case design spectrum is specifically prepared for a structure at a particular project site. the imposed load on roof need not be considered.3.3 The percentage of imposed loads given in 7.4.1. and (2) in 6. the earthquake force shall be calculated for the full dead load plus the percentage of imposed load as given in Table 8.3 Design Imposed Loads for Earthquakes Force Calculation 7. 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.3. I. 7.3. 7. stiffness and ductility.1.1. Where the probable loads at the time of earthquake are more accurately assessed. R.3.3.2 For calculating the design seismic forces of the structure.1 and 6. Buildings having simple regular geometry and uniformly distributed mass and stiffness in plan as well as in elevation.1. 7. for different building systems shall be as given in Table 7.3. and adequate lateral strength.3. a building should possess four main attributes. in load combinations (3) in 6. for different building systems shall be as given in Table 6. 7.2 where the gravity loads are combined with the earthquake loads [that is.Fig. 7. suffer much less damage than buildings with irregular configurations. if at least one of the conditions given in Tables 4 and 5 is applicable.1 Regular and Irregular Configuration To perform well in an earthquake.3.2 Importance Factor/and Response Reduction Factory The minimum value of importance factor.3.2 shall also be used for 'Whole frame loaded condition in the load combinations specified in 6.2]. the designer may alter the proportions indicated or even replace the entire imposed load proportions by the actual 24-20 .1 and 7.1.
2 only that part of imposed load. In such cases.assessed load.20 1. such as out-of-plane offsets of vertical elements Non-parallel System The vertical elements resisting the lateral force are not parallel to or symmetric about the major orthogonal axes or the lateral force resisting elements ii) iii) iv) v) 24-21 . While computing the seismic weight of each floor.00 0.3. where the imposed load is not assessed as per 7.1 and 7.3.2 times the average of the storey drifts at the two ends of the structure Re-entrant Corners Plan configurations of a structure and its lateral force resisting system contain re-entrant corners. The seismic weight of the whole building is the sum of the seismic weights of all the floors.70 0.3.5 Other loads apart from those given above (for example snow and permanent equipment) shall be considered as appropriate.60 0. or changes in effective diaphragm stiffness of more than 50 percent from one storey to the next Out-of-Plane Offsets Discontinuities in a lateral force resistance path.40 1. the weight of columns and walls in any storey shall be equally distributed to the floors above and below the storey.2. Torsional irregularity to be considered to exist when the maximum storey drift. 7.1 and 7. Lateral design force for earthquakes shall not be calculated on contribution of impact effects from imposed loads.2 Seismic Weight of Building.55 0. including those having cut-out or open areas greater than 50 percent of the gross enclosed diaphragm area. 7. 3) (Clause 1.2) 0 2 5 7 10 15 20 25 30 Damping Percent 3.4. which possesses mass.4. Where both projections of the structure beyond the re-entrant corner are greater than 15 percent of its plan dimension in the given direction Diaphragm Discontinuity Diaphragms with abrupt discontinuities or variations in stiffness.3 Any weight supported in between storeys shall be distributed to the floors above and below in inverse proportion to its distance from the floors.3. as specified in 7.1 Seismic Weight of floors The seismic weight of each floor is its full dead load plus appropriate amount of imposed load.1) SI. computed with design eccentricity. at one end of the structures transverse to an axis is more than 1.50 Factors Table 4 Definitions of Irregular Buildings — Plan Irregularities (Fig.80 0. No. Irregularity Type and Description (1) (2) i) 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. Table 3 Multiplying Factors for Obtaining Values for Other Damping (Clause 6.4.3. shall be considered. 7.4 Seismic Weight 7. 7.4.90 0.
No. such as hospitals. radio stations. tire station buildings. No.0 1. schools.1) SI. 4) (Clause 7. assembly halls and subway stations.2) SI. iii) iv) v) Table 6 Importance Factors. scaffolding etc of short duration. 2. The design engineer may choose values of importance factor I greater than those mentioned above. (1) ii) Irregularity Type and Description (2) Mass irregularity 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 storey lateral strength is the total strength of all seismic force resisting elements sharing the storey shear in the considered direction. (1) i) Structure (2) Important service and community buildings. I (Clause 6. (1) i) Irregularity Type and Description (2) a) Stiffness Irregularity . power stations All other buildings Importance Factor (3) 1. railway stations.4. This docs not apply to temporary structures like excavations. Buildings not covered in SI. depending on economy.5 ii) NOTES 1. (i) and (ii) above may be designed for higher value of I. 24-22 . The irregularity need not be considered in case of roofs Vertical Geometric Irregularity 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 In-Plane Discontinuity in Vertical Elements Resisting Lateral Force A in-plane offset of the lateral force resisting elements greater than the length of those elements Discontinuity in Capacity — Weak Strorey A weak storey is one in which the storey lateral strength is less than 80 percent of that in the storey above. large community halls like cinemas.Soft Starry A soft storey is one in which the lateral stillness is less than 70 percent of that in the storey above or less than 80 percent of the average lateral stillness of the three storeys above b) Stiffness Irregularity – Extreme Soft Storey A extreme soil 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.Table 5 Definition of Irregular Buildings — Vertical Irregularities (Fig. television stations. monumental structures. No. For example. buildings on STILTS will fall under this category Table 5 — Concluded SI. No. strategy considerations like multi-storey buildings having several residential units 3. emergency buildings like telephone exchange.
Fig. 3 Plan Irregularities – Continued 24-23 .
Fig. 4 Vertical Irregularities – Continued 24-24 .
Fig. 4 Vertical Irregularities 24-25 .
No.0 (iv) Steel moment resisting frame designed as per SP 6 (6) 5. R. 7) Ductile shear walls are those designed and detailed as per IS 13920.0 bars at comers of rooms and (vi) Ordinary reinforced concrete shear walls6) 3. 24-26 .5 b) Reinforced with horizontal RC bands 2.0 (iii) Steel frame with a) Concentric braces 4.5 (xi) Ductile shear wall with SMRF 5. and b) the moment resisting frames are designed to independently resist at least 25 percent of the design seismic base shear. 4) Buildings with shear walls also include buildings having shear walls and frames.0 7) 4. 8) Buildings with dual systems consist of shear walls (or braced frames) and moment resisting frames such that: a) the two systems arc designed to resist the total design force in proportion to their lateral stiffness considering the interaction of the dual system at all floor levels. but where: a) frames are not designed to carry lateral loads.15.Table 7 Response Reduction Factor1). and not just for the lateral load resisting elements built in isolation.5 c) Reinforced with horizontal RC bands and vertical 3. (1) Lateral Load Resisting System R (2) (3) Building Frame Systems (i) Ordinary RC moment-resisting frame (OMRF)2) 3.2) SI.0 (vii) Ductile shear walls Buildings with Dual System8) (viii) Ordinary shear wall with OMRF 3. 6) Prohibited in zones IV and V.4.0 Building with Shear Walls4) (v) Load bearing masonry wall buildings5) a) Unreinforced 1.0 (x) Ductile shear wall with OMRF 4. for Building Systems (Clause 6. or b) frames are designed to carry lateral loads but do not fulfil the requirements of ‘dual systems’.0 (ii) Special RC moment-resisting frame (SMRF)3) 5. 3) SMRF defined in 4.2. 2) OMRF are those designed and detailed as per IS 456 or IS 800 but not mooting ductile detailing requirement as per IS 13920 or SP 6 (6) respectively. 5) Reinforcement should be as per IS 4326.0 1) The values of response reduction factors are to be used for buildings with lateral load resisting elements.0 (ix) Ordinary shear wall with SMRF 4.0 b) Eccentric braces 5.
7.2. the total shear in any horizontal plane shall be distributed to the various vertical elements of lateral force 24-27 . along the considered direction of the lateral force. 7.1 In case of buildings whose floors are capable of providing rigid horizontal diaphragm action.0 2.6. in seconds.1 Buildings and portions thereof shall be designed and constructed. This design lateral force shall then be distributed to the various floor levels.2 The design lateral force shall first be computed for the building as a whole.1 The approximate fundamental natural period of vibration (Ta).1) Imposed Uniformity Percentage of Distributed Floor Imposed Load 2 Loads (kN/m ) (1) (2) Upto and including 3. hi = Height of floor i measured from base. in seconds.5.and b = Base dimension of the building at the plinth level. and n = Number of storeys in the building is the number of levels at which the masses arc located.75 for RC frame building = 0.09 Ta = d h = Height of building.3 shall be distributed along the height of the building as per the following expression: Qi = VB W1 hi2 The total design lateral force or design seismic base shear (VB) along any principal direction shall be determined by the following expression: V B = AhW Where Ah = Design horizontal acceleration spectrum value as per 6. in m. 7.7.2 Distribution of Horizontal Design Lateral Force to Different Lateral Force Resisting Elements 7.1. of a moment-resisting frame building without brick infil panels may be estimated by the empirical expression: Ta = 0.5 Above 50 7. to resist the effects of design lateral force specified in 7.2.5.3 Design Seismic Base Shear where h = Height of building.75 for steel frame building ∑W j =1 n j h2 j where Qi = Design lateral force at floor i. in m.4.1 Vertical Distribution of Base Shear to Different Floor Levels The design base shear VB computed in 7. 7.5.7. But. This excludes the basement storeys. 7.075 h0.6 in the considered direction of vibration.3 as a minimum. it includes the basement storeys. of all other buildings. in m.6. using the fundamental natural period Ta as per 7.3.5. Wi = Seismic weight of floor. when they are not so connected. 7.085 h0.7 Distribution of Design Force 7.2.Table 8 Percentage of Imposed Load to be Considered in Seismic Weight Calculation (Clause 7. including moment-resisting frame buildings with brick infil panels. and W = Seismic weight of the building as per 7.2 The approximate fundamental natural period of vibration (Ta).7.5. where basement walls are connected with the ground floor deck or fitted between the building columns.6 Fundamental Natural Period 7.4.5 Design Lateral Force 7.6. as defined in 7. may be estimated by the empirical expression: 0. The overall design seismic force thus obtained at each floor level shall then be distributed to individual lateral load resisting elements depending on the floor diaphragm action.
However.5 can be used. for the purposes of dynamic diaphragms.4.8. The analytical model for dynamic analysis of buildings with unusual configuration should be such that it adequately models the types of irregularities present in the building configuration. 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.8. in either method. assuming the floors to be infinitely rigid in the horizontal plane. the design base shear (VB) shall be compared with a base shear ( V B ) calculated using a fundamental period Ta.1 Dynamic analysis shall be performed to obtain the design seismic force.resisting system. shall be based on an appropriate ground motion and shall be performed using accepted principles of dynamics. analysis of steel and reinforced concrete buildings. not mandatory. lesser than 40 m in height in Zones II and III. all the response quantities (for example member forces.8.8. respectively.8 Dynamic Analysis 7.8.8.6.2 Dynamic analysis may be performed either by the Time History Method or by the Response Spectrum Method. storey shears and base reactions) shall be multiplied by V B VB . the lateral shear at each floor shall be distributed to the vertical elements resisting the lateral forces. displacements..5.1 Free Vibration Analysis Undamped free vibration analysis of the entire building shall be performed as per established methods of mechanics using the appropriate masses and elastic stiffness of the structural system. dynamic analysis. 7.4. is less than V B .8.1 The value of damping for buildings with topping reinforced screed can be taken a rigid may be taken as 2 and 5 percent of the critical. Where VB.2. even though recommended.2.4. b) Irregular buildings (as defined in 7.4. considering the in-plane flexibility of the diaphragms NOTES 1 A floor diaphragm shall be considered to be flexible. to obtain natural periods (T) and mode shapes {φ} of those of its modes of vibration that need to be considered as per 7.8.1).4.4. 7. and those greater than 90 m in height in Zones II and III.8.1 — All framed buildings higher than 12 m in Zones IV and V. is 2 Reinforced concrete monolithic slab-beam floors or those consisting of prefabricated/precast elements 7.4. Buildings with plan irregularities.2. spectrum mentioned in 6. and its distribution to different levels along the height of the building and to the various lateral load resisting elements. or by a sitespecific design.6. cannot be modelled for dynamic analysis by the method given in 7. for the following buildings: a) Regular buildings — Those greater than 40 m in height in Zones IV and V. storey forces. NOTE — For irregular buildings. and those greater than 40 m in height in Zones II and III. 7.2 In case of building whose floor diaphragms cannot be treated as infinitely rigid in their own plane. 7.2 Modes to be considered The number of modes to be used in the analysis should be such that the sum total 24-28 .4 Response Spectrum Method Response spectrum method of analysis shall be performed using the design spectrum specified in 6. 7. where Ta is as per 7. 7. Modelling as per 7. when used.2. 7.8. as defined in Table 4 (as per 7.3 Time History Method Time history method of analysis.7.
and 2 ⎡ n ⎤ ω j = Circular frequency in jth mode. storey shears and base reactions) shall be combined as per Complete where the summation-is for the closely Quadratic Combination (CQC) method.8. The effect of higher modes shall be included by considering where missing mass correction following well λk = Absolute value of quantity in mode k. established procedures. This peak response r r quantity due to the closely spaced modes λ = ∑∑ λi ρ ij λ j ( λ* ) is then combined with those of the i =1 j =1 remaining well-separated modes by the where method described in 7.2).of modal masses of all modes considered is a) If the building does not have closelyspaced modes. If modes with natural frequency beyond 33 Hz are to be considered.4. ρ ij = Cross-modal coefficient.8. In such a case. may be modelled as a system of masses λ j = Response quantity in mode j lumped at the floor levels with each mass (including sign). ⎢∑ Wi φ ik ⎥ ⎦ Alternatively. or λi = Response quantity in mode i nominally irregular.2.3 Analysis of building subjected to r = Number of modes being considered. then' the peak response at least 90 percent of the total seismic mass quantity (λ ) due to all modes and missing mass correction beyond 33 considered shall be obtained as percent. design forces The building may be analyzed by accepted b) If the building has a few closely-spaced modes (see 3. that of lateral displacement in the direction under 8 ζ 2 (1 + β ) β 1. having one degree of freedom.1. modal r combination shall be carried out only for λ = ∑ (λ k ) 2 k =1 modes upto 33 Hz. storey c forces. a) Modal Mass— The modal mass (Mk) of β = Frequency ratio = ω j ω i mode k is given by ω i = Circular frequency in ith mode.5 Buildings with regular.4. then the peak response principles of mechanics for the design forces considered as static forces. spaced modes only. displacements. quantity λ* due to these modes shall be Obtained as 7.8.4. r = Number of modes being considered.4.4 Modal combination r The peak response quantities (for example. plan configurations (including sign). (lie following ρ ij = (1 − β 2 ) 2 + 4 ζ 2 β (1 + β ) 2 expressions shall hold-in the computation of the various quantities: ζ = Modal damping ratio (in fraction) as specified in 7. the peak response quantities M = ⎣ i =1 may be combined as follows: k g ∑ Wi (φik ) 2 i =1 n 24-29 .8. and 7. λ* = ∑ λc member forces. 7.5 consideration.8.4 (a).
special arrangement needs to be forces Froof = Vroof and made to increase the lateral strength and stiffness of the soft/open storey.3 In case of highly irregular buildings mode k is given by n analyzed according to 7.1 Provision shall be made in all buildings for increase in shear forces on the stiffness effects of in fills and inelastic lateral force resisting elements resulting deformations in the members.4.5 represents dynamic amplification factor.2 Dynamic analysis of building is 7.05 represent d) Storey shear Forces in Each Mode – The the extent of accidental eccentricity. (Vi ) in storey I due to all modes considered 7.5.8. However. NOTE . design forces calculated as in 7.4.4.8. negative torsional shear b) Modal Participation Factors – The shall be neglected. such as the ground storey consisting f) Lateral Forces at Each Storey Due to All of open spaces for parking that is Stilt Modes Considered – The design lateral buildings.9.8.5 are to be applied al the centre of mass φik = Mode shape coefficient at floor i in appropriately displaced so as to cause mode k. The g = Acceleration due to gravity. natural period of vibration of mode k.05 bi ⎧ edi = ⎨ ⎩or e si − 0.10.from the horizontal torsional moment arising due to eccentricity between the centre of mass and centre of rigidity. 24-30 . e lo be where di Pk = ∑W (φ i =1 i i =1 n ∑W φ i n used at floor i shall be taken as: ik ik ) 2 1. peak shear force (Vik ) acting in storey i in 7.1 In case buildings with a flexible mode in accordance with 7.4.4.05b) with Considered – The peak storey shear force respect to the centre of rigidity. additive Vik = ∑ Qik shears will be superimposed for a statically j =i +1 e) Storey Shear Forces due to All Modes applied eccentricity of ± 0.2 using the perpendicular lo the direction of force.9.10 Buildings with Soft Storey is obtained by combining those due to each 7.2 The design eccentricity. Fi = Vi − Vi +1 7.05 bi c) Design Lateral Force at Each Floor in whichever of these gives the more severe Each Mode — The peak lateral force (Qik) effect in the shear of any frame where at floor i in mode k is given by edi = Static eccentricity at floor i defined as Qik = Ak φik Pk Wi the distance between centre of mass and centre of rigidity.10. particularly. and design eccentricity (7.2) between the Wi = Seismic weight of floor I displaced centre of mass and centre of rigidity.The factor 1.9 Torsion carried out including the strength and 7.9. while the (actor 0. storey.5 e si + 0. modal participation factor (Pk) of mode k is given by: 7.9. and where Ak = Design horizontal acceleration bi = Floor plan dimension of floor i spectrum value as per 6.
or two adjacent units of the same building with separation joint in between shall be separated by a distance equal to the amount R times the sum of the calculated storey displacements as per 7. (see 5.12. these are often designed only for the gravity loads.2 There shall be no drift limit for single storey building which has been designed to accommodate storey drift. individual spread footings or pile caps shall be interconnected with ties. in addition to the otherwise For building located in seismic Zones IV and V.those in the soft storey. Even though the slabs and columns are not required to share the lateral forces. while all the seismic force is reststed by the shear walls.1 of each of them. 7. in tension and in compression.1 the earthquake analysis. It is permissible lo use seismic force obtained from the computed fundamental period (T) of the building without the lower bound limit on design seismic force specified in 7.11. All ties shall be capable of carrying. cap load. an axial force equal to 7.12 Miscellaneous exceed 0 004 times the storey height.A /4 times the larger of the column or pile h Seismic Members.2 and 7.5 limes the storey shears and moments calculated under seismic loads specified in the oilier relevant clauses: or.11.2.12.1 Storey Drift Limitation factor R in this requirement may be The storey drill in any storey due to the replaced by R/2. Shear walls placed symmetrically in both directions of the building as far away from the centre of the building as feasible: lo be designed exclusively for 1 5 times the lateral storey shear force calculated is before 7.10. The concern is that under such deformations. detailed for the calculated storey shears and moments.2 Cantilever Projections 24-31 . In seismic Zones IV and V.8. it shall he ensured that the structural computed forces. the following design deformations equal to R times the storey criteria arc lo be adopted after carrying out displacements calculated as per 7.2 Deformation Compatibility of Non. a) the columns and beams of the soft storey arc to be designed for 2. IV and V. 7.11. the slab-column system should not b) besides the columns designed and lose its vertical load capacity. these deform with rest of the structure under seismic force.3 Alternatively. When floor levels of two similar adjacent units or buildings are at the same elevation levels. components. shall not 7.11.4. Here. Since the lateral resistance of the slab-column system is small.11.4.11. only).1 Foundations For the purposes of displacement requirements only (see 7. do not lose their vertical carrying capacity under the designed accordingly induced moments resulting from storey 7.1 of IS 4326) except when individual spread footings are directly supported on rock. 7.1. effect of infill walls in other storeys: Note: For instance consider a flat slab building in which lateral load resistance is provided by shear walls.3 Separation Between Adjacent Units Two adjacent buildings. The use of foundations vulnerable to significant differential settlement due to ground shaking shall be avoided for structures in seismic Zones III. minimum specified -design lateral force with partial load factor of 1 0. to avoid damaging contact when the two units deflect towards each other.11 Deformations 7. Ah is as per 6. neglecting the where R is specified in Table 7. that are not a part of the seismic force resisting system in the 7.11.3.11. and the members direction under consideration.3.
2.4. expect between the separation sections.2. Frictional resistance shall not be relied upon for fulfilling these requirements. such increase need not be considered. 7.2.3 Compound Walls Composed walls shall be designed for the design horizontal coefficient Ah with important factor I = 1. 7.2. smoke stacks (chimneys) and other vertical cantilever projections attached to buildngs and projecting above the roof.2 Horizontal projections All horizontal projections like cornices and balconies shall be designed and checked for stability for five times the design vertical coefficient specified in 6. 7.2.12.12.4. in all possible directions.2.4.1 and 7.12. parapets.2.12. In the analysis of the building.4 Connections Between Parts All parts of the building. tanks. shall be designed and checked for stability for five times the design horizontal seismic coefficient Ah specified in 6. shall be tied together to act as integrated single as beams to columns and columns to their footings.12.3 The increased design forces specified in 7.05 times the weight of the smaller part of the total of dead and imposed load reaction. For the design of the main structure.12. ANNEX A (Foreword) 24-32 .7.12. 7. Vertical projections Tower.2 are only for designing the projecting parts and their connections with the main structures. of magnitude (Qi Wi ) times but not less than 0. should be made capable of transmitting a force.1.0 specified in 6. the weight of these projecting elements will be lumped with the roof weight.5 (that is = 10/3 Ah).
24-33 . The interstate boundaries between Arunachal Pradesh. 1971. but have yet to be verified. The external boundaries and coastlines of India agree with the Record/Master Copy certified by Survey of India.Based upon Survey of India with the permission of the Surveyor General of India. The administrative headquarters of Chandigarh. The responsibility for the correctness of internal details rests with the publisher. Assam and Meghalaya shown on this map are as interpreted from the North-Eastern Areas (Reorganization) Act. The territorial waters of India extend into the sea to distance of twelve nautical miles measured from the appropriate base line. Haryana and Punjab are at Chandigarh.
Assam and Meghalaya shown on this map are as interpreted from the North-Eastern Areas (Reorganization) Act. The interstate boundaries between Arunachal Pradesh. The administrative headquarters of Chandigarh. The external boundaries and coastlines of India agree with the Record/Master Copy certified by Survey of India. The territorial waters of India extend into the sea to distance of twelve nautical miles measured from the appropriate base line. 24-34 . Haryana and Punjab are at Chandigarh. The responsibility for the correctness of internal details rests with the publisher. but have yet to be verified. 1971.ANNEX B (Foreword) Based upon Survey of India map with the permission of the Surveyor General of India.
The external boundaries and coastlines of India agree with the Record/Master Copy certified by Survey of India. but have yet to be verified.ANNEX C (Foreword) Based upon Survey of India map with the permission of the Surveyor General of India. 24-35 . Assam and Meghalaya shown on this map are as interpreted from the North-Eastern Areas (Reorganization) Act. The territorial waters of India extend into the sea to distance of twelve nautical miles measured from the appropriate base line. 1971. The responsibility for the correctness of internal details rests with the publisher. The interstate boundaries between Arunachal Pradesh. The administrative headquarters of Chandigarh. Haryana and Punjab are at Chandigarh.
Hanging objects swing considerably. 4. pan tiles slip off cracks in chimneys parts of chimney fill down. Grade 3 Heavy damage Large and deep cracks in plaster: fall of chimneys Grade 4 Destruction Gaps in walls: part of buildings may collapse: separate pans or the buildings lose their cohesion: and inner wills collapse 5. outdoors by few. Grade 2 Moderate damage Small cracks in plaster. rural structures. Weak. Occasionally pendulum clocks stop. outdoors by many. Many people awake A few run outdoors Animals become uneasy. Reinforced buildings. Here and there people awake. buildings of large block and prefabricated type. outdoors only in favorable circumstances the vibration is like that due to the passing of a light truck. Pictures knock against walls or swing out of place. Attentive observers notice a slight swinging of hanging objects. 2.The intensity of the vibration is below the limits of sensibility: the tremor is detected and recorded by seismograph only. Though not finally approved the scale is more comprehensive and describes the intensity of earthquake more precisely. Floors and walls crack Furniture begins to shake Hanging objects swing slightly. Ordinary brick buildings. few About 5 percent Many Most About 50 percent About 75 percent c) Classification of Damage to Buildings Grade 1 Slight damage Fine cracks in plaster. Largely observed — The earthquake is felt indoors by many people. well built wooden structures. half timbered structures. In standing motor cars the shock is noticeable Type B Type C b) Definition of Quantity: Single. especially on upper floors of buildings. doors. somewhat more heavily on upper floors. Awakening i) The earthquake is felt indoors by all. buildings in natural hewn stone. but no one is frightened The vibration is like that due to (lie passing of a heavily loaded truck. Liquids spill in small 24-36 . clay houses. Fall of small pieces of plaster. Liquid in open vessels arc slightly disturbed. Windows. 3. Unstable objects overturn or shift Open doors and windows are thrust open and slam back again.15) COMPREHENSIVE INTENSITY SCALE (MSK64) The scale was discussed generally at the intergovernmental meeting convened by UNESCO in April 1964. fall of fairly large pieces of plaster. Not noticeable . Building tremble throughout. partially observed only — The earthquake is felt indoors by a few people.ANNEX C (Foreword and Clause 3. Grade 5 Total damage Total collapse of the buildings d) Intensity Scale 1. Scarcely noticeable (very slight) Vibration is felt only by individual people at rest in houses. The main definitions used arc followings: a) Type of Structures (Buildings) Type A Building in field-stone. and dishes rattle. unburnt-brick houses.
heavy objects falling inside the buildings. crack in roads. and books fall down. individual cases. Most Many people in buildings are frightened buildings of Type B suffer damage of and run outdoors. on slopes and springs changes. 9. and a few of Grade 4. Domestic animals run out of llicir damage of Grade 4. A few persons loose their Grade 3. Dry wells iii) In few cases. Destruction of buildings i) Fright and panic. The vibration is noticed by persons ii) Many buildings of Type C suffer driving motor cars. Heavy furniture may possibly move and Stonewalls collopse. confusion. Frightening ii) Most buildings of Type C suffer damage i) Felt by most indoors and outdoors. ii) In many buildings of Type C damage of damage of Grade 3. 6. in mountains many cases. steep slopes. change in flow of water is observed. have their flow resorted and existing a large number of slight cracks in ground. falls of rock. made turbid by mud stirred up. change in flow and level of occasional landslips.amounts from well-filled open containers. In isolated instances The sensation of vibration is like that due to parts of sand and gravelly banks slip off. railway lines are bent and iii) Waves arc formed on water. sand and mud is often observed. landslides of roadway on Considerable damage to reservoirs. reservoirs come into existence. 8. also persons driving ii) Slight damages in buildings of Type A motor cars arc disturbed. small steeple bells may ring. springs stop flowing. Some limes dry springs riverbanks more than 10 cm. branches of trees break off. In few instances. New Type A is of Grade 2. Grade 1 is caused. iii) Small landslips in hollows and on ii) Damage of Grade 1 is sustained in single banked roads on sleep slopes. Monuments and columns fall. In cm possible in wet ground. many landslides and earth 24-37 . Most of Grade 4 and a few of Grade 5. few of Grade 4. cracks in buildings of Type B and in many of ground upto widths of several centimeters. Here and three are possible. Even heavy iii) Sometimes changes in flow of springs furniture moves and partly overturns. Hanging lamps arc damaged in pan. Many find it difficult to stand. Further more. Water iii) On flat land overflow of water. and cry. Large bells ring. and is roadway damaged. instances. dishes and pipe seams Memorials and monuments glassware may break. Occasional breaking of stalls. Many buildings of Type A suffer damage of buildings of Type A suffer damage of Grade 3. of Grade 2 and few of Grade 3. springs and in level of well water are observed. Most buildings of Type A suffer balance. General damage of buildings 7. considerable damage to i) Most people are frightened and run furniture. Damage of buildings i) General panic. Animals run to and fro in outdoors. and llic flow of to widths of up to 10 cm. In pipelines damaged: cracks in stonewalls. scams of underground pipes partly broken. move and twist Tombstones overturn. Type A Damage in few buildings of Water in takes become turbid. Ground cracks levels in wells change. in many buildings of Many buildings of Type B show a damage Type B damage is of Grade 2. In single Grade 5. cracks up to widths of 1 refill and existing wells become dry.
16 0.16 0. as well as movement in Grade 5.24 0.24 0.10 0. Highways become useless. thrown on land New lakes Lakes are dammed. and a few of Grade 5. cracks up to widths of several i) Practically all structure above and below centimeters.16 0. Dry wells i) Severe damage even to well built renew their flow and existing wells dry up.10 0.16 0. Parallel ground are greatly damaged or destroyed. ANNEX E (Foreword) ZONE FACTORS FOR SOME IMPORTANT TOWNS Town Agra Ahmedabad Ajmer Allahabad Almora Ambala Amritsar Asansol Aurangabad Bahraich Bangalore Barauni Bareilly Bhatinda Bhilai Bhopal Bhubaneswar Zone III III II II IV IV IV III II IV II IV III III II II III Zone Factor. Landscape changes ii) In ground. sometimes up to I in.16 0. The intensity of the earthquake requires to be investigated 11. Destruction specially. change of movements are observed. Most of Type A have destruction of cracks and fissures. Z 0.24 0.10 0. General destruction of buildings i) Many buildings of Type C suffer damage Underground pipes destroyed.16 0. Underground pipes the earthquake requires to be investigated arc bent or broken. rivers. asphalt show waves.10 0. buildings. water dams and railway lines. Many buildings of Type B show damage of Grade ii) Ground considerably distorted by broad 5. Loose ground slides from steep slopes.10 0. From ii) The surface of the ground is radically riverbanks and sleep coasts. Numerous dams.36 0. Road paving and specifically.10 24-38 .24 0. Considerable ground cracks with landslides arc possible.16 0. extensive vertical and horizontal displacement of sand and mud.10 0. Z 0. etc.16 Town Chitradurga Coimbatore Cuddalore Cuttack Darbhanga Darjeeling Dharwad Dehra Dun Dharampuri Delhi Durgapur Gangtok Goa Gulbarga Gaya Gorakhpur Hyderabad Zone II III III III V IV III IV III IV III IV III II III IV II Zone Factor. lakes. Critical damage to dykes and horizontal and vertical direction.24 0. bridges.16 0.24 0.24 0.24 0. In coastal areas.16 0. considerable changed.16 0. 12. Severe damage to bridges. of Grade 4. waterfalls appear and occur rivers are deflected.24 0. 10.flows. to watercourses occur broad fissures. The intensity of lines are bent slightly. Railway landslips and falls of rocks.10 0. Falling of rock water level in wells.16 0.16 0.16 0.24 0. large waves in water.10 0. and slumping of riverbanks over wide areas. water from canals.
36 0.36 0.16 0.16 0.16 0.16 0.24 0.36 0.24 0.24 Imphal Jabalpur Jaipur Jamshedpur Jhansi Jodhpur Jorhat Kakrapara Kalapakkam Pondicherry Pune Raipur Rajkot Ranchi Roorkee Roukela Sadiya Salem Simla Sironj Solapur Srinagar Surat Tarapur Tezpur Tnane Tanjavur Thiruvananthapuram Tiruchirappali Tiruvennamalai Udaipur Vadodara Varanasi Vellore Vijayawada Vishakhapatnam V III II II II II V III III II III II III IV IV II V III IV II III V III III V III II III II III II III III III III II 0.Bhuj Bijapur Bikaner Bokaro Bulandshahr Burdwan Cailcut Chandigarh Chennai Kanchipuram Kanpur Karwar Kohima Kolkata Kota Kurnool Lucknow Ludhiana Madurai Mandi Mangalore Monghyr Moradabad Mumbai Mysore Nagpur Nagarjunasagar Nainital Nasik Nellore Osmanabad Panjim Patiala Patna Patna Pilibhit V III III III IV III III IV III III III III V III II II III IV II V III IV IV III II II II IV III III III III III IV IV IV 0.24 0.10 0.16 0.16 0.16 0.10 0.24 0.10 0.24 0.10 24-39 .36 0.10 0.24 0.10 0.16 0.24 0.24 0.36 0.10 0.16 0.16 0.16 0.10 0.10 0.16 0.16 0.16 0.16 0.16 0.16 0.36 0.10 0.10 0.24 0.10 0.10 0.16 0.24 0.36 0.16 0.16 0.16 0.16 0.36 0.10 0.16 0.10 0.10 0.16 0.16 0.16 0.16 0.10 0.16 0.16 0.10 0.24 0.16 0.16 0.16 0.16 0.16 0.
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