Jan 22, IS (Part 1) Indian Standard CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES PART 1 GENERAL. Is (Part 1) Indian Standards Criteria for Earthquake Resistant Design of Structures Part 1 - Download as PDF File .pdf), Text File .txt) or read online. IS (Part 1): Indian Standard. CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES PART 1 GENERAL PROVISIONS AND .
|Language:||English, Spanish, French|
|Genre:||Business & Career|
|ePub File Size:||16.85 MB|
|PDF File Size:||10.59 MB|
|Distribution:||Free* [*Register to download]|
IS (Part 1) Indian Standard. CRITERIA FOR EARTHQUAKE RESISTANT. DESIGN OF STRUCTURES. PART 1 GENERAL. PROVISIONS. code, IS (Part 1): The Indian seismic code IS has now been split into a number of parts and the first part containing general provisions. IS (): Criteria for Earthquake Resistant Design of Structures, Part 1: General Provisions and Buildings. [CED Earthquake Engineering].
Himalayan-Nagalushai region, Indo-Gangetic Plain, Western India, Kutch and Kathiawar regions 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 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 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 IS brought out in
It covers general principles and design criteria, combinations, design spectrum, main attributes of buildings, dynamic analysis, apart from seismic zoning map and seismic coefficients of important towns, map showing epicenters, map showing tectonic features and lithological map of India.
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. Here it is worthwhile to mention that 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 endeavoured to ensure that as far as, possible structures are able to respond, without structural damage to shocks of moderate intensities and without total collapse to shocks of heavy intensities.
In addition to the above, stack-like structures covered by this standard are such as transmission and communication towers, chimneys and stack-like structures and silos including parabolic silos used for urea storage. The characteristics intensity, duration, etc of seismic ground vibrations expected at any location depends upon the magnitude of earthquake, its depth of focus, distance from the epicenter, characteristics of the path through which the seismic waves travel, and the soil strata on which the structure stands.
The response of a structure to ground vibrations is a function of the nature of foundations, 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, liquify or slide due to loss of strength during vibrations. The design approach adopted in this standard is to ensure that structures possess minimum strength to withstand minor earthquakes DBE which occur frequently, without damage; resist moderate earthquakes DBE without significant structural damage though some non-structural damage may occur; and withstand a major earthquake MCE without collapse.
In this standard, it is intended to cover the specified features of design and construction for earthquake resistance of buildings of conventional types. No special provisions are considered necessary in Zone II. However, considering inherently weak against water and earthquake, earthen buildings should preferably be avoided in flood prone, high rainfall areas and seismic zones IV and V. Table 6 Importance Factors. The irregularity need not be considered in case of roofs iii 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 percent of that in its adjacent storey iv In-Plane Discontinuity Resisting Lateral Force in Vertical Elements A in-plane offset of the lateral force resisting elements greater than the length of those elements v 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.
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. I Clause 6. Torsional irregularity to be considered to exist when the maximum storey drift.
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. The overall design seismic force thus obtained at each floor level. This design lateral force shall then be distributed to the various floor levels. If modes with natural frequency beyond 33 Hz are to be considered. 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.
Undamped free vibration analysis of the entire The effect of higher modes shall be included by considering missing mass correction following well established procedures. NOTE — For irregular buildings. Modelling as per 7. Buildings with plan irregularities.
Where VB is less than V B all the response quantities for example member forces. Response spectrum method of analysis shall be performed using the design spectrum specified in 6. In such a case. The design forces calculated as in 7. Froof and Fi. There shall be no drift limit for single storey building which has been designed to accommodate storey drift. Ah is as per 6. All ties shall be capable of carrying. The concern is that under such deformations.
In seismic Zones IV and V. In the analysis of the building. Since the lateral load resistance of the slab-column system is small. Even though the slabs and columns are not required to share the lateral forces. IV and V. When floor levels of two similar adjacent units or buildings are at the same elevation levels.
All connections between different parts. For the design of the main structure. Frictional resistance shall not be relied upon for fulfilling these requirements.
Haryana and Punjab are at Chandigarh. The interstate boundaries between Arunachal Prades. The territorial waters of India extend into the sea to distance of twelve nautical miles measured from the appropriate base line.
The responsibility for the correctness of internal details rests with the publisher. The administrative headquarters of Chandigarh. Copyright Year Slight damages in buildings of Type A are possible. A few run outdoors. Pictures knock against walls or swing out of place. Hanging objects swing slightly. Many people awake.
The vibration is like that due to the passing of a heavily loaded truck. Not noticeable — The intensity of the vibration is below the limits of sensibility. The main definitions used are followings. Attentive observers notice a slight swinging of hanging objects. Furniture begins to shake. Type B — Ordinary brick buildings.
Hanging objects swing considerably. Though not finally approved the scale is more comprehensive and describes the intensity of earthquake more precisely. Grade 4 Destruction Grade 5 Total damage 5. Open doors and windows are thrust open and slam back again. Floors and walls crack. Grade 3 Heavy damage Large and deep cracks in plaster. Largely observed — The earthquake is felt indoors by many people.
The earthquake is felt indoors by all. Occasionally pendulum clocks stop. The sensation of vibration is like that due to heavy objects falling inside the buildings. Liquids spill in small amounts from well-filled open containers.
Awakening i Gaps in walls. Scarcely noticeable very slight — Vibration is felt only by individual people at rest in houses. Liquid in open vessels are slightly disturbed. In standing motor cars the shock is noticeable. Grade 2 Moderate damage Small cracks in plaster. The vibration is like that due to the passing of a light truck.
Here and there people awake. Building tremble throughout. Type C — Reinforced buildings. Animals become uneasy. Unstable objects overturn or shift. Loose ground slides from steep slopes. Here and there branches of trees break off. Further more.
Water levels in well change. From river banks and steep coasts. Dry wells refill and existing wells become dry. Many buildings of Type A suffer damage of Grade 5. Most buildings of Type B suffer damage of Grade 3. Hanging lamps are damaged in part. Destruction of buildings i Fright and panic. Considerable damage to reservoirs. Underground pipes are bent slightly. Dry wells renew their flow and existing wells dry up.
In individual cases. Critical damage to dykes and dams.
Occasional breaking of pipe seams. In few instances. New lakes occur.
In many cases. Underground pipes are bent or broken. Damage in few buildings of Type A is of Grade 2. A few persons loose their balance. Road paving and asphalt show waves. Railway lines are bent slightly. Most of Type A have destruction of Grade 5.
Highways become useless In isolated instances parts of sand and gravelly banks slip off. Monuments and columns fall. In single instances. Animals run to and fro in confusion. Frightening i Felt by most indoors and outdoors. General damage of buildings i General panic. Ground cracks to widths of up to 10 cm. Parallel to water courses occur broad fissures.
Large bells ring. Stone walls collapse. Even heavy furniture moves and partly overturns. Most buildings of Type A suffer damage of Grade 4. Destruction i Severe damage even to well built buildings. Water in lakes become turbid. Many buildings of Type B show damage of Grade 5. Damage of buildings i Most people are frightened and run outdoors. Memorials and monuments move and twist. Some times dry springs have their flow resorted and existing springs stop flowing. Heavy furniture may possibly move and small steeple bells may ring.
Many people in buildings are frightened and run outdoors. Many buildings of Type B show a damage of Grade 4 and a few of Grade 5. Tombstones overturn. Domestic animals run out of their stalls. New reservoirs come into existence. Severe damage to bridges. Most buildings of Type A suffer damage of Grade 3. General destruction of buildings i Many buildings of Type C suffer damage of Grade 4.
Many find it difficult to stand.
The fourth revision, brought out in , 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. Hence, IS has been split into the following five parts: Part 1 General provisions and buildings Part 2 Liquid retaining tanks — 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.
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. The following are the major and important moditlcations made in the fifth revision: Erstwhile Zone I has been merged to Zone 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. J Modal combination rule in dynamic analysis of buildings has been revised. 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.
For guidance on precautions to be observed in the construction of buildings, reference maybe made to IS , IS and IS Earthquake can cause damage not only on account 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. In the seismic zoning map, Zone I and II of the contemporary map have been merged and assigned the level of Zone 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 seismic hazard level with respect to ZPA at 50 percent risk level and 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. 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.
The Sectional Committee responsible for the formulation of this standard has attempted to include a seismic zoning map see Fig. 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 maximum seismic ground acceleration in each zone cannot be presently predicted with 3 5. 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. 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: Commentary, Report No.
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: The number of signflcant places retained in the rounded off value should be the same as that of the specified value in this standard.
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. 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 Application of plastic theory in design of steel structures Code of practice for general construction in steel second revision Earthquake resistant design and construction of buildings — Code of practice second revision Title revision Code of practice for design loads other than earthquake for buildings and structures: Part l: IS Part: 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. 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. 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. Force It is the horizontal seismic force prescribed by this standard, that shall be used to design a structure. 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.
Ductility of a structure, or its members, is the capacity to undergo large inelastic deformations without significant loss of strength or stiffness. The maximum response is plotted against the undamped natural period and for various damping values, and can be expressed in terms of maximum absolute acceleration, maximum relative velocity, or maximum relative displacement. The modal mass for a given mode has a unique value irrespective of scaling of the mode shape.
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.
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. 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. It is the value of acceleration response spectrum for period below 0. Spectrum The representation of the maximum response of 9 It is part of the structural system assigned to resist lateral forces. This point corresponds to the centre of gravity of masses of system. It is a frame in which members and joints are capable of resisting forces primarily by flexure.
The point through which the resultant of the restoring forces of a system acts. It is a moment-resisting frame specially detailed to provide ductile behaviour and comply with the requirements given in IS or IS or SP6 6. 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. 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 4. It is the difference in levels between the base of the building and that of floor i.
It is the displacement of one level relative to the other level above or below. It is the space between two adjacent floors. Coefficient used in the Complete Quadratic Combination CQC method while combining responses of modes i andj Reinforced and prestressed concrete members shall be suitably designed to ensure that premature failure due to shear or bond does not occur, subject to the provisions of IS and IS 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 members for which load combinations that do not contain the earthquake effect indicate larger demands than combinations including earthquake.
The soil-structure interaction may not be considered in the seismic analysis for structures supported 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 members and of cantilevered members.
Hence, special attention should be paid to the effect of vertical component of the ground motion on prestressed or cantilevered beams, girders and slabs.
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.
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 account, load combinations specified in 6. In important cases, it may be necessary to obtain floor response spectra for design of equipment supports.
For detail reference be made to IS Part 4.