FAILURE OF FOUNDATION DUE TO EARTHQUAKE

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As we know, shaking due to seismic waves causes damage to buildings. The damage may be influenced by the characteristics of soil in the affected area. The objective of the paper is to show the effect of the earthquake on different types of foundations such as shallow, mat/raft, pile and structures like gravity dam, arch dam etc. The reaction of soil to the loading of the building when a building undergoes an earthquake disturbance as a behaviour of deflection is known as the soil structure interaction. The movement of ground during the Earthquake induces kinematic and inertial loading which decreases the bearing capacity and increments the settlement of shallow foundations. In seismic regions, where kinematic interactions have been observed, the mat foundations experiences overturning moments. Pile foundations are influenced by both kinematic and inertial interactions which causes many failures. The convoluted oscillating arrangement of acceleration and ground motion in a gravity dam, developing ephemeral dynamic loads because of inertia of dam and confined water is the seismic activity generated in these dams. The arch dam foundations undergoes effects of inertia and flexibility due to the propagation of seismic waves.

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i A Project Report on FAILURE OF FOUNDATION DUE TO EARTHQUAKE Submitted by: KURESH CHANDRA TRIPATHY 1301210349 SUBIN KUMAR BEHERA 1301210457 SURAJ KUMAR AGRAWAL 1301210527 ABHISHEK KUMAR SAHU 1301210573 SATYAJIT BEHERA 1301210657 In partial fulfilment for the award of the Degree Of BACHELOR OF TECHNOLOGY IN CIVIL ENGINEERING Under the esteemed guidance of Miss. TRUPTIMALA PATTNAIK ASST. HOD CIVIL AT DEPARTMENT OF CIVIL ENGINEERING GANDHI INSTITUTE OF ENGINEERING AND TECHNOLOGY GUNUPUR – 765022 2013-2017

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ii DECLARATION We hereby declare that the project entitled “FAILURE OF FOUNDATION DUE TO EARTHQUAKE” submitted for the B. Tech Degree is my original work and the project has not formed the basis for the award of any degree associate-ship fellowship or any other similar titles. Signature of the Students: 1. 2. 3. 4. 5. Place: Date

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iii Gandhi Institute of Engineering Technology GUNUPUR – 765 022 Dist: Rayagada Orissa India Approved by AICTE Govt. of Orissa and Affiliated to BijuPatnaik University of Technology : 06857 – 250172Office 251156Principal 250232Fax e-mail: gandhi_gietyahoo.com visit us at www.giet.org ISO 9001:20001 Certified Institute CERTIFICATE This is to certify that the project report entitled “FAILURE OF FOUNDATION DUE TO EARTHQUAKE” submitted by KURESH CHANDRA TRIPATHY 1301210349 SUBIN KUMAR BEHERA 1301210457 SURAJ KUMAR AGRAWAL 1301210527 ABHISHEK KUMAR SAHU1301210573 SATYAJIT BEHERA1301210657 to the Biju Patnaik University of Technology Rourkela Odisha in partial fulfilment for the award of Degree of Bachelor of Technology in Civil engineering is a bonafide record of the project work carried out by him under my supervision during the year 2016-2017. To the best of our knowledge the results embodied in this dissertation have not been submitted to any University/Institute for the award of any other degree. Mr. ASHIS KUMAR SAMAL Prof. XYZ Miss. TRUPTIMALA PATTNAIK Professor and Head Asst. Prof. CIVIL Project guide HODCIVIL Department of Mechanical Engineering EXTERNAL EXAMINER

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4 ACKNOWLEDGEMENTS It is a great pleasure and privilege to express my profound sense of gratitude to our esteemed guide HOD Mr. ASHIS KUMAR SAMAL Asst. HOD Miss. TRUPTIMALA PATTAN all the teachers for their suggestions motivation and support during the project work and keen personal interest throughout the progress of my project work. I express my thanks to all my friends my family for their timely suggestions and encouragements. KURESH CHANDRA TRIPATHY 13CV001 SUBIN KUMAR BEHERA 13CV011 SATYAJIT BEHERA 13CV019 SURAJ KUMAR AGRAWAL 13CV029 ABHISHEK KUMAR SAHU 13CV032

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5 Abstract As we know shaking due to seismic waves causes damage to buildings. The damage may be influenced by the characteristics of soil in the affected area. The objective of the paper is to show the effect of the earthquake on different types of foundations such as shallow mat/raft pile and structures like gravity dam arch dam etc. The reaction of soil to the loading of the building when a building undergoes an earthquake disturbance as a behaviour of deflection is known as the soil structure interaction. The movement of ground during the Earthquake induces kinematic and inertial loading which decreases the bearing capacity and increments the settlement of shallow foundations. In seismic regions where kinematic interactions have been observed the mat foundations experiences overturning moments. Pile foundations are influenced by both kinematic and inertial interactions which causes many failures. The convoluted oscillating arrangement of acceleration and ground motion in a gravity dam developing ephemeral dynamic loads because of inertia of dam and confined water is the seismic activity generated in these dams. The arch dam foundations undergoes effects of inertia and flexibility due to the propagation of seismic waves.

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6 CONTENT Title Page  AKNOWLEDGMENT  ABSTACT  LIST OF FIGURE  ABBREVIATIONS  NOMECLATURE 1. INTRODUCTION 09 2. DEFINATION OFFOUNDATION ITS TYPES 10 2.1 Types of earthquake 2.1.1 Tectonic 10 2.1.2 Volcanic 11 2.1.2 Collapse and explosion 11 2.1.3 Measurement of earthquake 12 2.1.4 Characterises of earthquake 12 2.1.5 Seismic zones 13 2.2 Types of foundation 2.2.1 Shallow foundation 15 2.2.2 Deep foundation 16 3. FAILURE OF FOUNDATION 17 4. GENERAL PRINCIPLE AND DESIGN CRITERIA 22 2.4.1 General principles 5. THE SOIL STRUCTURE INTERACTION 23 5.1 Addition to existing structures 24 5.2 Change in occupancy 24 5.2.1 Assumptions 5.3 Load combination and increase in permissible stresses 25 5.3.1 Load combinations 5.3.2 Load factors for plastic design of steel structures 25 5.3.3 Design horizontal earthquake load 26 5.3.4 Design vertical earthquake load 26 5.3.5 Combination for two or three component motion 26

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7 5.4 Increase in permissible stresses 5.4.1 Increase in permissible stress in materials 27 5.4.2 Increase in allowable pressure in soils 6. GENERAL PRINCIPLE AND DESIGN CRITERIA 6.1 Design spectrum 28 6.2 Design lateral force 32 6.2.1 Design seismic base shear 33 6.3 Fundamental natural period 33 6.4 Distribution of design force 34 6.5 Buildings with soft storey 35 6.6 Deformation 6.6.1 Storey drift limitation 6.6.2 Deformation compatibility of non-seismic members 36 6.6.3 Separation between adjacent units 36 7. CONCLUSION 40 8. REFERENCE 41

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8 List of figure SL. Title Page No. 1 Image of tectonic earthquake 10 2 Image of volcanic earthquake 11 3 Figure of an explosion earthquake 11 4 Details of earthquake zone in India 14 4 Shallow foundation 15 5 Deep foundation 16 6 Post earthquake pile configuration 18 7 Building at SanFernado Vally hall California earthquake 19 8 Crossection of pile configuration of Rokko Island 20 9 Waterfront side exposing foundation elements 21 10 Beam-to-column stiffness ratio 22 11 Relative distribution of story shear 37

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9 INTRODUCTION A member of a structure that connects it to the ground and distribute loads to the ground is Foundation. There are different types of foundation for different purposes. Modern types of foundation are Shallow foundation and Deep foundation. 3Foundations are constructed to bear sufficient load capacity depending on the type of subsoil aiding the foundation. The settling of the foundation below the level of initial construction to a point where damage has already been happened is known as foundation failure. The extent of damage ensuing from earthquakes in the earthquake affected area is stimulated by the behaviour of the soil. Here the damage is linked to the overall vulnerability of the soil which leads to enormous permanent movements of the lower surface. Thus for an example deposition of granular soils is compressed by the vibrations caused by the earthquake that develops massive and differential settlements in the lower surface. During earthquake the soil consisting of loose granular materials leads to inclination and settlement of structures. The soil-structure interaction SSI influences the structures seismic response. Collapse of buildings resting on piles in damp soils are noticed after most earthquakes like the survey after 1995 Kobe earthquake Niigata earthquake in 1964 and the 2001 Bhuj earthquake the application to the ground motion for site specific SSI analysis is presented. In several earthquake-prone regions shallow foundations are used for small size structures. The bearing capability of a shallow foundation is decreased when the horizontal loads and rocking moments acts on the foundation. The reaction of pile during seismic loading includes the evaluation of kinematic curving that occurs due to the sideward displacement of a pile along with the mechanical phenomenon forces acting on the cap mass that imitates the structure. Here we discuss about the impact of earthquake on different types of foundation.

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10 Definition:- Earthquake: An earthquake also known as a quake tremor or temblor is the shaking of the surface of the Earth resulting from the sudden release of energy in the Earths lithosphere that creates seismic waves. Foundation: A foundation or more commonly base is the element of an architectural structure which connects it to the ground and transfers loads from the structure to the ground Types of earthquake:- 1. Tectonic 2. Volcanic 3. Collapse and explosion o A tectonic earthquake is one that occurs when the earths crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.

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11 o A volcanic earthquake is any earthquake that results from tectonic forces which occur in conjunction with volcanic activity. o A collapse earthquake are small earthquakes in underground caverns and mines that are caused by seismic waves produced from the explosion of rock on the surface. o An explosion earthquake is an earthquake that is the result of the detonation of a nuclear and/or chemical device.

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12 Measurement of Earthquakes:- Earthquake strength is commonly measured in two ways: with the Richter scale and with the Modified Mercalli Intensity Scale. The Richter scale measures magnitude as an indirect measure of released energy based on instrument recordings according to certain defined procedures. The scale runs from zero at the low end and is open at the upper end although the largest earthquake ever recorded had a Richter magnitude of nine. The scale is logarithmic each whole number value on the scale represents a tenfold increase in amplitude. In terms of energy released each scale number represents about 32 times the amount of energy below it. The Modified Mercalli Intensity Scale is a measure of an earthquake’s intensity. It is an entirely subjective rating based on the observed damage to structures and other physical effects. The scale ranges from I to XII with the upper rating being the most severe. Each scale includes a verbal description of the effects and damage of an earthquake. The Modified Mercalli Scale is imprecise because it depends on people’s observations but it does provide information on how an earthquake affects structures and how the same earthquake affects areas at different distances from the epicentre both of which cannot be accounted for with the Richter scale. Unfortunately for building design neither scale is useful. This is because neither provides any information on the acceleration or duration of an earthquake both of which are critical in the analysis and design of structures. However they are used for risk analysis and determination of seismic zones. Objective quantified data useful for building design is provided by the strong motion accelerograph. This machine measures the acceleration of the ground or a building. The BIS requires that in seismic zones 3 and 4 every building over 6 stories with an aggregate floor area of 60000 square feet or more and every building over 10 stories regardless of floor area be provided with not less than three accelerographs. These must be placed in the basement midportion and near the top of the building. Some jurisdictions may have additional requirements. The records obtained by these instruments provide valuable data for research and design of similar buildings in the same geographical area. The acceleration they measure is usually expressed as a fraction of the acceleration of gravity g which is 32 feet per second per second. Thus an earthquake may be recorded as having an acceleration of 0.55g. Characteristics of Earthquakes:- Earthquakes are caused by the slippage of adjacent plates of the earth’s crust and the subsequent release of energy in the form of ground waves. Seismology is based on the science of plate tectonics which proposes that the earth is composed of several very large plates of hard crust many miles thick riding on a layer of molten rock closer to the earth’s core. These plates are slowly moving relative to one another and over time tremendous stress is built up by friction. Occasionally

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13 the two plates slip releasing the energy we know as earthquakes. One of the most well known boundaries between two plates occurs between the Pacific plate and the North American plate along the coast of California. Earthquakes also occur in midplates but the exact mechanism other than fault slippage is not fully understood. The plates slip where the stress is maximum usually several miles below the surface of the earth. Where this occurs is called the hypocenter of the earthquake. The term heard more often is the epicenter which is the point on the earth’s surface directly above the hypocenter. When an earthquake occurs complex actions are set up. One result is the development of waves that ultimately produce the shaking experienced in a building. There are three types of waves: P or pressure waves S or shear waves and surface waves. Pressure waves cause a relatively small movement in the direction of wave travel. Shear waves produce a sideways or up-and-down motion that shakes the ground in three directions. These are the waves that cause the most damage to buildings. Surface waves travel at or near the surface and can cause both vertical and horizontal earth movement. The ground movement can be measured in three ways: by acceleration velocity and displacement. All three occur over time with most earthquakes lasting only a few seconds. It is the acceleration of the ground that induces forces on a structure. The interaction of the various waves and ground movement is complex. Not only does the earth move in three directions but each direction has a different random acceleration and amplitude. In addition the movement reverses creating a vibrating action. Even though there is vertical movement the BIS allows it to be neglected under certain types of seismic design. The weight of a structure is usually enough to resist vertical forces. It is the side- to-side movement that causes the most Seismic Zones:- Based on seismic records experience and research some areas of the India are determined to have a greater probability of earthquakes than others and some areas have more severe earthquakes areas where two major plates abut for example. This is taken into account by dividing the country into different zones that represents times of future earthquake occurrence and strength. The map used by the BIS is shown in Figure . The procedure for incorporating the zones will be discussed in a later section.

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14 Bureau of Indian Standards Criteria for earthquake resistant design of structures IS 1893 : 2002

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15 Types of foundation:- Foundations are generally considered either shallow or deep. Shallow foundation: Shallow foundations often called footings are usually embedded about a metre or so into soil. One common type is the spread footing which consists of strips or pads of concrete or other materials which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock. Another common type of shallow foundation is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed at the surface. Slab-on-grade foundations can be reinforced mat slabs which range from 25 cm to several meters thick depending on the size of the building or post-tensioned slabs which are typically at least 20 cm for houses and thicker for heavier structures.

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16 Deep foundation: A deep foundation is used to transfer the load of a structure down through the upper weak layer of topsoil to the stronger layer of subsoil below. There are different types of deep footings including impact driven piles drilled shafts caissons helical piles geo-piers and earth stabilized columns. The naming conventions for different types of footings vary between different engineers. Historically piles were wood later steel reinforced concrete and pre-tensioned concrete.

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17 FAILURE OF FOUNDATION:- Failure in foundations can be due to various reasons such as Lateral movement of soil adjacent to the structure Unequal settlement of sub-soil Overturning of the structure due to lateral pressure Unequal settlement of the masonry contraction due to removal of moisture from the soil beneath the foundation Action of atmosphere Lateral escape of the soil below the foundation etc. The effects of foundation failures can range from bulging floors to cracked walls to displaced mouldings. The external signs are wall rotation cracked and/or broken foundation separation around garage door windows and/or walls cracked bricks. While the internal hints are cracks on floors disordered door sand windows broken sheetrock. The ground deformations which are permanent completely break the structure. Some foundation types can resist these permanent ground deformity. Most damage in a building is a result of ground movement. The building’s foundations vibrate in the same way as the surrounding ground when the ground shakes at the building site. The building reaction to an earthquake movement occurs over a few seconds. During this time many kinds of seismic waves combine to vibrate the building in ways that are distinct in detail. Additionally as an outcome of various geological nature of every site deviations in fault seepage different rocks in which the waves travel overall shaking at every site is different. The aspect of every buildings are varied in method of analysis configuration dimension age architectural system or quality of construction. The above aspects affects the reaction of the building. Instead of the complex nature of the interactions among the building and ground within the few seconds of movement there is wide understanding of how differently building types can perform under the different conditions. During earthquakes when external forces act on the system neither the structural displacements nor ground displacements are independent of each other.

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18

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19 Building at San Fernando Valley Juvenile Hall pulled apart by lateral spread during 1971 San Fernando California earthquake Les Youd photo

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20 Cross section showing pile configuration for a building on Rokko Island Kobe Japan. Area was shaken by 1995 Kobe Japan Earthquake. Liquefaction and ground settlement average 0.75 m occurred without significant structural damage to buildings on pile foundations. Piles have proven effective structural mitigation measure against liquefaction at sites with tolerable lateral ground displacement

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21 Waterfront side of Ferry Building showing pavement that settled and pulled away from building due to liquefaction and lateral spread exposing foundation elements

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22 Moment frame with small beam-to-column stiffness ratio and b equivalent static lateral force distribution from dynamic analysis and IBC expression Chopra 2005. GENERAL PRINCIPLES AND DESIGN CRITERIA General Principles: Ground Motion 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 epicentre characteristics of the path through which the seismic waves travel and the soil strata on which the structure stands. The random earthquake ground motions which cause the structure to vibrate can be resolved in any three mutually perpendicular directions. The predominant direction of ground vibration is usually horizontal. Earthquake-generated vertical inertia forces are lo be considered in design unless checked and proven In 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

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23 cases of prestressed horizontal membe 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. The response of a structure to ground vibration is a function of the nature of foundation soil: materials from size and mode of construction of structures and the duration and characteristics of ground motion I Ins standard specifies design forces for structures standing on rocks or soils which do not settle liquefy or slide due to loss of strength during ground vibrations. The design approach adopted in tins standard is to ensure that structures possess at least a 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 aims that structures withstand a major earthquake MCE without collapse Actual forces that appear on structures during earthquakes are much greater than the design forces specified in this standard However ductility arising from inelastic material behaviour and detailing and over strength arising from the additional reserve strength in structures over and above the design strength are relied upon to account for this difference in actual and design lateral loads. 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 456 and IS 1343. Provisions for appropriate ductile detailing of reinforced concrete members arc given in IS 13920. In steel structures members and their connections should be so proportioned that high ductility is obtained. Avoiding premature failure due to elastic or inelastic buckling of any type. The specified earthquake loads are based upon post-elastic 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. Soil Structure interaction:- The soil-structure interaction refers to the effects of the supporting foundation medium on the motion of structure. The soil-structure interaction may not be considered in the seismic analysis for structures supported on rock or rock-like material. The design lateral force sped tied in this standard shall lie considered in each of lie two orthogonal horizontal directions of the structure. For structures which have lateral force resisting elements in the two orthogonal directions only the design lateral force shall be considered along one direction at a time and not in

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24 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 tin load combinations Where both horizontal and vertical seismic forces are taken into account load combinations shall be considered. Equipment and oilier systems which are supported al various floor levels of the structure will be subjected to motions corresponding to vibration al their support points. In important cases it may be necessary to obtain floor response spectra for design of equipment supports. 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. 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 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 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. Change in Occupancy When a change of occupancy results in a structure being re-classified to a higher importance factor I the structure shall conform to the seismic requirements for a new structure with the higher importance factor.

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25 Assumptions:- The following assumptions shall be made in the earthquake resistant design of structures: a Earthquake causes impulsive ground motions which are complex and irregular in character changing in period and amplitude each lasting for a small duration. Therefore resonance of the type as visualised under steady-state sinusoidal excitations will not occur as it would need time to build up such amplitudes. b Earthquake is not likely to occur simultaneously with wind or maximum flood or maximum sea waves. c The value of elastic modulus of materials wherever required may be taken as for static analysis unless a more definite value is available for use in such condition Load Combination and Increase in Permissible Stresses Load Combinations When earthquake forces are considered on a structure these shall be combined. Where the terms DL IL and EL stand for the response quantities due to dead load imposed load and designated earthquake load respectively. Load factors for plastic design of steel structures: In the plastic design of steel structures the following load combinations shall be accounted for: 1 1.7 DL + IL 2 1.7 DL ± EL 3 1.3 DL + IL ± EL

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26 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 the following load combinations shall be accounted for: 1 1.5 DL + L 2 l.2 OL + IL ± EL 3 l.5 DL ± EL 4 Q.9DL ± l.5EL Design Horizontal Earthquake Load: When the lateral load resisting elements are oriented along orthogonal horizontal direction the structure shall be designed for the effects due to full design earthquake load in one horizontal direction at time. When the lateral load resisting elements are not oriented along the orthogonal horizontal directions the structure shall be designed for the effects due to full design earthquake load in one horizontal direction plus 30 percent of the design earthquake load in the other direction. Design Vertical Earthquake Load: When effects due to vertical earthquake loads are to be considered the design vertical force shall be calculated in accordance. Combination for Two or Three Component Motion: When responses from the three earthquake components are to be considered the responses due to each component may be combined using the assumption that when the maximum response from one component occurs the responses from the other two component are 30 percent of their maximum. All possible combinations of the three components ELx ELy and ELz including variations in sign plus or minus shall be considered. Thus the response due earthquake force EL is the maximum of the following three cases:

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27 1 ± ELx ± 0.3 Ely ± 0.3 ELz 2 ± ELy ± 0.3 ELx ± 0.3 ELz 3 ± ELz ± 0.3 ELx ± 0.3 ELy where x and y are two orthogonal directions and z is vertical direction. As an alternative to the procedure in the response EL due to the combined effect of the three components can be obtained on the basis of square root of the sum of the square SRSS’ that is √ 2 + 2 + 2 When two component motions say one horizontal and one vertical or only two horizontal are combined the equations should be modified by deleting the term representing the response due to the component of motion not being considered. Increase in Permissible Stresses: Increase in permissible stresses in materials:- When earthquake forces are considered along with other normal design forces the permissible stresses in material in the elastic method of design may be increased by one-third. However for steels having a definite yield stress the stress the stress limited to the yield stress for steels without a definite yield point the stress will be limited to 80 percent of the ultimate strength or 0.2 percent proof stress whichever is smaller and that in prestressed concrete members the tensile stress in the extreme fibers of the concrete may be permitted so as not to exceed two-thirds of the modulus of rupture of concrete. Increase in allowable pressure in soils: When earthquake forces are included the allowable bearing pressure in soils shall be increased as per Table 1 depending upon type of foundation of the structure and the type of soil. In soil deposits consisting of submerged loose sands and soils falling under classification SP with standard penetration N-values less than 15 in seismic Zones III IV V and less than 10 in seismic Zone II the vibration caused by earthquake may cause liquefaction or excessive total and differential settlements. Such sites should preferably be avoided while locating new settlements or important projects. Otherwise this aspect of the problem needs to be investigated and appropriate methods of compaction or stabilization adopted to achieve suitable N-values as indicated in Note 3 under Table 1. Alternatively

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28 deep pile foundation may be provided and taken to depths well into the layer which is not likely to liquefy. Marine clays and other sensitive clays are also known to liquefy due to collapse of soil structure and will need special treatment according to site condition. Design Spectrum: For the purpose of determining seismic forces the country is classified into four seismic zones. The design horizontal seismic coefficient for a structure shall be determined by the following expression: ℎ 2 Provided that for any structure with T≤ 0.1 s the value of h A will not be taken less than Z/2 whatever be the value of where Z Zone factor given in Table 2 is for the Maximum Considered Earthquake MCE and service life of structure in a zone. The factor 2 in the denominator of Z is used so as to reduce the Maximum Considered Earthquake MCE zone factor to the factor for Design Basis Earthquake DBE. I Importance factor depending upon the functional use of the structures characterised by. hazardous consequences of its failure post earthquake functional needs historical value or economic importance. R Response reduction factor depending on the perceived seismic damage performance of the structure characterised by ductile or brittle deformations. However the ratio I/R shall not be greater than 1.0 Table 7. The values of R for buildings are given in Table 7. /g Average response acceleration coefficient

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29 Table-1 Percentage of Permissible Increase in Allowable Bearing Pressure or Resistance of Soils

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30 Table-2 Zone factor Seismic II III IV V Zone Seismic Low Moderate Severe Very Intensity Severe Z 0.10 0.16 0.24 0.36 for rock or soil sites based on appropriate natural periods and damping of the structure. Where a number of modes are to be considered for dynamic analysis the value of Ah. For each mode shall be determined using the natural period of vibration of that mode. For underground structures and foundations at depths of 30 m or below the design horizontal acceleration spectrum value shall be taken as half the value obtained. For structures and foundations placed between the ground level and 30 m depth the design horizontal acceleration spectrum value shall be linearly interpolated between Ah and 0.5 Ah Where ℎ 2 The design acceleration spectrum for vertical motions when required may be taken as two-thirds of the design horizontal acceleration spectrum. 5 percent spectra for rocky and soils sites and Table 3 gives the multiplying factors for obtaining spectral values for various other dampings.

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31 In case design spectrum is specifically prepared for a structure at a particular project site the same may be used for design at the discretion of the project authorities. Table 3 Multiplying Factors for Obtaining Values for Other Damping Damping 0 2 5 7 10 15 20 25 30 Percent Factors 3.20 1.40 1.00 0.90 0.80 0.70 0.60 0.55 0.50

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32 Design Lateral Force: Buildings and portions thereof shall be designed and constructed to resist the effects of design lateral force as a minimum. The design lateral force shall first be computed for the building as a whole. This design lateral force shall then be distributed to the various floor levels. The overall design seismic force thus obtained at each floor level shall then be distributed to individual lateral load resisting elements depending on the floor diaphragm action. Another difficulty with seismic design is that the forces produced by an earthquake are so great that no building can economically and reasonably be designed to completely resist all loads in a major earthquake without damage. Building codes and analytical methods of design are therefore a compromise between what could resist all earthquakes and what is reasonable. Because of this the current approach in designing earthquake resistant structures is that they should first of all not collapse during major seismic activity. Additionally the components of buildings should not cause other damage or personal injury even though they may be structurally damaged themselves. Finally structures should be able to withstand minor earthquakes without significant damage. The analyatic methods of analysis and design of earthquake-resistant structures are complex even with the simplified static analysis method allowed by the Uniform Building Code BIS. However a great deal of resistance is provided by the basic configuration and structural system of a building. The design of buildings for earthquake loads requires an early and close collaboration between the architect and engineer to arrive at the optimum structural design while still satisfying the functional and aesthetic needs of the client. This chapter will discuss some of the basic principles of earthquakes and the primary design and planning guidelines with which you should be familiar. In addition a basic review of the static analysis method will

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33 be presented along with some simplified problems to help explain the design concepts. Design Seismic Base Shear: The total design lateral force or design seismic base shear VB along any principal direction shall be determined by the following expression: ℎ Where ℎ Design horizontal acceleration spectrum value W Seismic weight of the building. Fundamental Natural Period The approximate fundamental natural period of vibration Ta in seconds of a moment-resisting frame building without brick infil panels may be estimated by the empirical expression: 0.075ℎ 0.75 for RC frame building 0.085ℎ 0.75 for steel frame building where h Height of building in m. This excludes the basement storeys where basement walls are connected with the ground floor deck or fitted between the building columns. But it includes the basement storeys when they are not so connected. The approximate fundamental natural period of vibration Ta in seconds of all other buildings including moment-resisting frame buildings with brick infil panels may be estimated by the empirical expression: 0.09 √ h Height of building in m b Base dimension of the building at the plinth level in m along the considered direction of the lateral force.

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34 Distribution of Design Force Vertical Distribution of Base Shear to Different Floor Levels: The design base shear computed by formula ℎ shall be distributed along the height of the building as per the following expression: Where Design lateral force at floor i Seismic weight of floor ℎ Height of floor i measured from base and n Number of storeys in the building is the number of levels at which the masses arc located. Distribution of Horizontal Design Lateral Force to Different Lateral Force Resisting Elements: In case of buildings whose floors are capable of providing rigid horizontal diaphragm action the total shear in any horizontal plane shall be distributed to the various vertical elements of lateral force resisting system assuming the floors to be infinitely rigid in the horizontal plane. In case of building whose floor diaphragms cannot be treated as infinitely rigid in their own plane the lateral shear at each floor shall be distributed to the vertical elements resisting the lateral forces considering the in-plane flexibility of the diaphragms.

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35 Buildings with Soft Storey: In case buildings with a flexible storey such as the ground storey consisting of open spaces for parking that is Stilt buildings special arrangement needs to be made to increase the lateral strength and stiffness of the soft/open storey. Dynamic analysis of building is carried out including the strength and stiffness effects of in fills and inelastic deformations in the members particularly those in the soft storey and the members designed accordingly Alternatively the following design criteria arc lo be adopted after carrying out the earthquake analysis neglecting the effect of infill walls in other storeys: a the columns and beams of the soft storey arc to be designed for 2.5 limes the storey shears and moments calculated under seismic loads specified in the oilier relevant clauses: b besides the columns designed and detailed for the calculated storey shears and moments. Shear walls placed symmetrically in both directions of the building as far away from the centre of the building as feasible: lo be designed exclusively for 1 5 times the lateral storey shear force calculated is before. Storey Drift Limitation: The storey drill in any storey due to the minimum specified -design lateral force with partial load factor of 1 0. shall not exceed 0.004 times the storey height. For the purposes of displacement requirements only 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. There shall be no drift limit for single storey building which has been designed to accommodate storey drift. MAXIMUM INTERSTORY DRIFT DISTRIBUTIONS:- Since the suggested lateral force distribution is based on inelastic response the structures designed by using such distribution tend to be better proportioned. In other words the possibility of overdesign or underdesign in certain regions is greatly reduced. Figure 6 shows that an EBF designed by using the suggested lateral force distribution.

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36 Deformation Compatibility of Non-Seismic Members: For building located in seismic Zones IV and V it shall he ensured that the structural components that are not a part of the seismic force resisting system in the direction under consideration do not lose their vertical carrying capacity under the induced moments resulting from storey deformations equal to R times the storey displacements calculated. Where R is taken from the table below. Separation between Adjacent Units: Two adjacent buildings 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 of each of them to avoid damaging contact when the two units deflect towards each other. When floor levels of two similar adjacent units or buildings are at the same elevation levels factor R in this requirement may be replaced by R/2.

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37 On the other hand the suggested lateral force distribution thus the relative story shear distribution is closer to the results obtained from nonlinear dynamic analyses. It is noted as shown in Figure 6 that relative story shear distribution using α 0.5 generally represents a lower bound of the nonlinear dynamic analysis results. This would normally lead to larger design forces at upper floors which may result in concentration of inelastic deformation at the lower levels. Further analyses by Chao and Goel 2005 and 2006a show that relative story shear distribution using α 0.75 represents an upper bound of the nonlinear dynamic analysis results Figure 6 and generally leads to more uniform deformations of elements as well as stories over the height of the structure which will be discussed later. Figure 6. Relative story shear distributions from nonlinear dynamic analyses code expressions and suggested expression for nine-story moment frame designed based on NEHRP expression.

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38 ZONE FACTORS FOR SOME IMPORTANT TOWNS Town Zone Zone Town Zone Zone Factor Factor Z Z Agra III 0.16 Chitradurga II 0.10 Ahmedabad III 0.16 Coimbatore III 0.16 Ajmer II 0.10 Cuddalore III 0.16 Allahabad II 0.10 Cuttack III 0.16 Almora IV 0.24 Darbhanga V 0.36 Ambala IV 0.24 Darjeeling IV 0.24 Amritsar IV 0.24 Dharwad III 0.16 Asansol III 0.16 Dehra Dun IV 0.24 Aurangabad II 0.10 Dharampuri III 0.16 Bahraich IV 0.24 Delhi IV 0.24 Bangalore II 0.10 Durgapur III 0.16 Barauni IV 0.24 Gangtok IV 0.24 Bareilly III 0.16 Goa III 0.16 Bhatinda III 0.16 Gulbarga II 0.10 Bhilai II 0.10 Gaya III 0.16 Bhopal II 0.10 Gorakhpur IV 0.24 Bhubaneswar III 0.16 Hyderabad II 0.10 Bhuj V 0.36 Imphal V 0.36 Bijapur III 0.16 Jabalpur III 0.16 Bikaner III 0.16 Jaipur II 0.10 Bokaro III 0.16 Jamshedpur II 0.10 Bulandshahr IV 0.24 Jhansi II 0.10 Burdwan III 0.16 Jodhpur II 0.10 Cailcut III 0.16 Jorhat V 0.36 Chandigarh IV 0.24 Kakrapara III 0.16 Chennai III 0.16 Kalapakkam III 0.16 Kanchipuram III 0.16 Pondicherry II 0.10 Kanpur III 0.16 Pune III 0.16

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39 Karwar III 0.16 Raipur II 0.10 Kohima V 0.36 Rajkot III 0.16 Kolkata III 0.16 Ranchi IV 0.24 Kota II 0.10 Roorkee IV 0.24 Kurnool II 0.10 Roukela II 0.10 Lucknow III 0.16 Sadiya V 0.36 Ludhiana IV 0.24 Salem III 0.16 Madurai II 0.10 Simla IV 0.24 Mandi V 0.36 Sironj II 0.10 Mangalore III 0.16 Solapur III 0.16 Monghyr IV 0.24 Srinagar V 0.36 Moradabad IV 0.24 Surat III 0.16 Mumbai III 0.16 Tarapur III 0.16 Mysore II 0.10 Tezpur V 0.36 Nagpur II 0.10 Tnane III 0.16 Nagarjunasagar II 0.10 Tanjavur II 0.10 Nainital IV 0.24 Thiruvananthapuram III 0.16 Nasik III 0.16 Tiruchirappali II 0.10 Nellore III 0.16 Tiruvennamalai III 0.16 Osmanabad III 0.16 Udaipur II 0.10 Panjim III 0.16 Vadodara III 0.16 Patiala III 0.16 Varanasi III 0.16 Patna IV 0.24 Vellore III 0.16 Patna IV 0.24 Vijayawada III 0.16 Pilibhit IV 0.24 Vishakhapatnam II 0.10

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40 The solutions to prevent the damage are:- 1 The super structure is tied to the foundation so that the entire structure acts as a single unit. 2 The building can be floated above its foundation which is known as base isolation. Resulting to which lateral acceleration is decreased and the structure experiences far less deformity and damage. However the structure still can receive fixed amount of vibrational energy during seismic loading even with base isolation system in place. The building itself can drench this energy to some level however its capability to do so is proportionate with the ductile nature of the material used during construction. Presently materials such as combination of rubber and steel plates are invented which are used on buildings to absorb the vibration due to the Earthquake. These are few ways by which we could prevent some losses during earthquakes in future. Earthquakes cannot be stopped but we can learn more in aspiration of discovering new ways to protect ourselves from their dangerous effects. Simple precautions are most effective ways to minimise Earthquake damage. CONCLUSION:- The effect of earthquake on the foundation of different architectural structures are influenced in a number of ways by the nature and the behaviour of the soils in the affected area. In spite of modern Engineering technology the complete structure may collapse in an earthquake if the foundation of the structure lies on soft soil. However the geotechnical engineers can incredibly enhance the structure how the structure and foundation together react to the seismic waves.

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41 References:- 1 wikipedia.org 2 Indian Standard criteria for earthquake resistant design of structures Part1 general provisions and buildings fifth Revision 3 Tokimatsu K. Suzuki H. Sato M." Effects of inertial and kinematic interaction on seismic behaviour of pile with embedded foundation " Nishikameya 1501-21 Shijimi MIki-shi Hyogo-ken 673-0515 Japan November2004. 4 Roy D." Design Of Shallow And Deep Foundations For Earthquakes" Geotechnical Earthquake Engineering Design of Shallow and Deep Foundations for Earthquakes. IIT Gandhinagar – March 2013 5 Lou M.Wang H.Chen X.Zhai Y. "Structure–soil structure interaction: Literature review" Elsevier Ltd. Amsterdam August2011 6 Trombetta W.N. Mason B. HutchinsonC.T. ZupanD.BrayD.J .Kutter L.B. " Nonlinear Soil Foundation–Structure and Structure–Soil–Structure Interaction: Engineering Demands"J. Struct. Eng. 2014. 7 Bureau of Indian standards criteria for earthquake resistant design of structure IS 1813:2002 8 Rai D. C. Goel S. C. and Firmansjah J. 1996. SNAP-2DX: General Purpose Computer Pro-gram for Static and Dynamic Nonlinear Analysis of Two Dimensional Structures Report No. UMCEE 96-21 Department of Civil and Environmental Engineering University of Michi-gan Ann Arbor

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