Literature Review of Methods for Earthquake Analysis

Literature Review of Methods for earthquake AnalysisCHAPTER 22. bungholevass OF LITERATURE2.1 INTRODUCTIONEarthquakes result from the sudden movement of tectonic plates in the earths crust. The movement takes place at fault lines, and the energy released is transmitted through the earth in the form of waves that causes res publica motion m each an opposite(prenominal) miles from the epicenter. Regions adjacent to active fault lines argon the most prone to experience quake. As the commonwealth moves, inertia tends to keep construction in place, resulting in the double- spileing of shifts and forces that crumb consider catastrophic results. The decision of the seismal fig is to semblance structures so that they give the gate withstand the slips and the forces induced by the ground motion. seismal initiation has emphasised the effects of horizontal ground motion, because the horizontal components of an quake usually exceed the plumb component and because structur es ar usually untold stiffer and squiffyer in resolution to vertical effects than they ar in repartee to horizontal loads.Any acquire process has assorted components through which learning takes place. School learning whitethorn be based on appropriate knowledge, theoretical explanations and look at, but most people learn more from genuine examples and learning by doing. Seeing is as well as much more educative than just reading, reason for which the illustration of a topic is of great wideness to the learning process. Analysing post earthquake pictures does vividly teach about what ends were bad and why. Unfortunately, that skunknot be verbalize from the structures that were not damaged because from the outside little can be seen. Only the require of the drawings and calculations can determine why a certain structure did not fail, and while neighbouring structure were damaged or thoroughly catch ond. In particular those wrenchs that are at the point of tota l failure are interesting because they present themselves as a kibosh pitch during the process of collapsing.Earthquake engineers in recent years discombobulate emphasized the need for military operation-based seismal summary. An infixed element in many unstable evaluations is the determination of ultimate inelastic reaction of the structure. Performance-based method actings require mediocre estimates of inelastic crookedness or damage in structures which are purify quantities to assess damage than stress or forces. The exercise based digest is based on quantifying the deformation of the members and the nosepiece circuit structure as a whole, under the lateral forces of an earthquake of a certain level of seismic hazard. Existing codes are based on elastic abridgment which has no measure of the deformation capability of members of brace circuits. The performance based digest gives the psychoanalyst more choice of performance of the brace circuits as compared to the coif states of collapse and serviceability in a endeavor based on limit state method.Flexibility of soil causes lengthening of lateral natural plosive speech grievous due to oerall decrease in lateral stiffness of the morphologic system. Such lengthening of lateral natural period whitethorn advantageously alter the seismic response of the create frames resting on isolated foundation. great amount of works have been carried out in the above said areas by look forers. In the present work, a few literatures related to these areas are reviewed and reported.2.2 CODAL PROVISIONS FOR PERFORMANCE BASED ANALYSISThe FEMA-273 (1997) archive provides technically sound and acceptable guidelines for the seismic rehabilitation of buildings. The guidelines for the seismic Rehabilitation of Buildings are intend to practise as a ready tool for design professionals, a reference document for building regulatory officials, and a foundation for the afterlife extendment and implementation of building code provisions and standards. This document provides different Seismic performance levels of buildings for morphologic and Non-structural components in detail. It also gives different compend physical processs use for Seismic rehabilitation of buildings.The FEMA-349 (2000) action plan presents a sage and cost useful approach by which building stakeholders owners, financial institutions, engineers, architects, contractors, researchers, the unrestricted and governing agencies, leave behind be able to move to a performance based design and evaluation system. The plan recognizes that there is a strong demand from stakeholder groups for more reliable, quantifiable and practical means to control building damage. It also recognizes that there is not a foc employ representing among these groups as to how these goals can be obtained. This Plan describes how performance based seismic design guidelines can be developed and employ to achieve these goals. It engages each o f the groups in the development of these guidelines, by which future building design will drive more efficient and reliable.The FEMA-356 (2000) standard is intended to serve as a nationally applicable tool for design professionals, code officials, and building owners attempt the seismic rehabilitation of real buildings. The subroutines contained in this standard are specifically applicable to the rehabilitation of existing buildings and are, in general, more appropriate for that purpose than are new building codes. Advancement of present-generation performance-based seismic design procedures is widely recognized in the earthquake engineering community as an essential next step in the nations drive to develop resilient, loss- repellant communities.FEMA 445 (2006) course of instruction plan offers a step-by-step, task-oriented program that will develop next-generation performance-based seismic design procedures and guidelines for structural and nonstructural components in new a nd existing buildings. This program plan is a refinement and extension of devil earlier FEMA plans FEMA 273 Performance- ground Seismic Design of Buildings an Action Plan, which was prepared by the Earthquake Engineering query Center, University of California at Berkeley in 1997, and FEMA 349 Action Plan for Performance Based Seismic Design, which was prepared by the Earthquake Engineering Research take in 2000. The state of practice for performance-based perspicacity, performance-based design of new buildings, and performance-based upgrades of existing buildings will all be significantly advanced under this Program Plan.ATC-40 (1996) document provides a comprehensive, technically sound recommended methodology for the seismic evaluation and provide design of existing concrete buildings. Although it is not intended for the design of new buildings, the analytical procedures are applicable. The document applies to the overall structural system and its elements and components. Th e methodology utilise here is performance based the evaluation and retrofit design criteria are expressed as performance markives, which defines desired levels of seismic performance when the building is subjected to specified levels of seismic ground motion. Acceptable performance is heedful by the level of structural and/or non-structural damage expected from the earthquake shaking. Damage is expressed in terms of post yield, inelastic deformation limits for different structural components and elements found in concrete buildings. The analytical procedure incorporated in the methodology accounts for post elastic deformations of the structure by employ simplified nonli tight static analysis methods.IRC 6 The object of the cadence Specifications and Code of Practice is to establish a common procedure for the design and construction of road bridgeworks in India. This publication is meant to serve as a guide to both the design engineer and the construction engineer but complian ce with the rules therein does not relieve them in any way of their responsibility for the stability and soundness of the structure designed and erected by them. The design and construction of road bridge require an considerable and through knowledge of the science and technique involved and should be entrusted scarce to pickyly qualified engineers with adequate practical experience in bridge engineering and capable of ensuring careful execution of work.IS 1893 (Part 3) 2002 The standard (Part 3) deals with the assessment of earthquake forces and design of new bridges on highways, railways, flyover bridges, pedestrian bridges, submergible bridges, utility bridges and aqueducts. The earthquake effect on retaining walls and bridge abutments are covered. The hydrodynamic effect of water on submerged substructure and method of assessment of liquefaction potential of soil is also included. The methodology of estimation of seismic forces given in the code can be employed for seismic evaluation of the existing bridges and retrofitting of such structures.This standard deals with the earthquake resistant design of regular bridges in which the seismic actions are chiefly resisted at abutments or through flexure of piers, that is, bridges composed of vertical pier-foundation system supporting the deck structure with/without bearings. However for all special and major bridges, detailed dynamic studies should be undertaken.This standard does not deal with the construction features relating to earthquake resistant design of bridges.RESPONSE SPECTRUM ANALYSISGreg wire-haired pointing griffon and M. Saiid Saiidi, have made a study to better infer the bridge response due to turn up response effect. Several methods are visible(prenominal) to predict bridge response to incoherent ground motions, but are typically cost prohibitive to implement in standard bridge designs. To simplify the analysis and understand the pseudo-static displacement and acceleration demeanour, they developed a response history computer fashion model for a two form of freedom (DOF) system. A super structure of a bridge is equal by shear beam connected both DOF. They used principle of superposition of the pseudo-static and acceleration response in order to determine the total DOF response. The site response effect was predicted by a SDOF, nonlinear ground response model. An iteration scheme using the Newton-Raphson method was implemented and it has been verified with an combining weight linear stiffness method. Later Parametric studies were conducted on different structure masses and shear beam stiffnesses. For varied soil depths at supports, they used three different earthquake ground motions. A stiffness statement defined as Coupling Ratio (CR) varies from 0 (each DOF responds independently) to 1 (rigid consistency response) has been observed. Then the magnification factors were calculated as the ratio of the relative displacement at each DOF due to the incoherent g round motion to the unvaried base motion response. They observed from the study that magnification factors could be used to account for ground motion incoherency by modifying the response of a two DOF system subjected to uniform base motion.Said M. Allam and T. K.Datta , studied on response spectrum method of analysis for abatement bridges subjected to multicomponent, partially gibe stationary ground motion. This analysis conducted is based on the relationship amid the situation spectral density function and the response spectrum of the input ground motion and fundamentals of the frequency domain spectral analysis. They said that analysis duly takes into account the spatial correlation of ground motions between the supports, also the quasi-static component of the response, and the modal correlation between different modes of vibration. They have examine the suspension bridge under a set of important parametric variations to study (1) The comparison between the responses obtain ed by the response spectrum method of analysis and the frequency domain spectral analysis and (2) To investigate the carriage of suspension bridges under seismic excitation. The parameters defined in analysis include the spatial correlation of ground motion, the ratio between the three components of ground motion, the angle of incidence of the earthquake, the nature and number of modes considered in the analysis, and the nature of the power spectral density function of ground motion. They finally think that the response spectrum method of analysis provides a fair estimate of responses under parametric variations considered in the study.TIME HISTORY ANALYSISYong Deng, a senior structural engineer has made a research on seismic issues over structures. He studied that Non-linear m history Analysis simulates the structure behavior under severe Earthquake movement pick outly than any other methods. In his paper, Non-linear time history analysis has been presented with one of the worl d notable project. Yerba Buena Island (YBI) West-Bound (WB) Ramps are portion of San Fransisco-Oakland Bay Bridge Project. The ramps are touched chain reactor to Yerba Buena Island from YBI WB widening by hinges. . This project is located at a 0.627g situation Specific Response for Safety Evaluation Earthquake (SEE). YBI WB On-ramp is a highly horizontally Curved Bridge with radius of 38.8 meters. He mentioned that Seismic behavior is very important for the project. In order to understand structural non-linear behavior, especially highly horizontally curved bridge behavior under severe earthquake events, YBI WB On-ramp stand-alone bridge is canvass by non-linear time history analysis method. A analysis software SAP 2000 with Hilber-Hughes-Taylor direct integration method is used for Non-linear Time explanation Analysis. Seismic Modeling is also discussed in this paper. Then he has used six sets of acceleration time histories for Non-linear Time autobiography Analysis by SAP 2000. to a fault a program developed by University of California-Berkeley is used to verify Non-linear Time history Analysis accuracy in this paper. Site Specific Response Spectra ARS is also used for liner analysis and compared with results of Non-linear Time History Analysis and with the program developed by California-Berkeley University. Later the Non-linear push-over analysis is performed to determine the structural capacity and ductility under severe earthquake events. Finally, discrepancies between different program analyses are discussed and recommendations are presented.R. K. Dowell, has studied on a new method for finding member forces for statically indeterminate bridge frames. He said that the unique aspect of this new method is that it produces exact member-end-moments for statically indeterminate bridge frames from simple closed-form equations, without the need to setup and solve a system of simultaneous equations, as required in the stiffness method. Also the result s hows that new method is 1000 times faster than any of the currently useable methods that depend on matrix manipulation. He presented the additive form of the closed-form approach and nonlinear time-history results for a typical bridge frame subjected to earthquake loading are compared with the results obtained from stiffness method. Finally he concluded that new closed form approach is based on modify classical analysis techniques and is so fast and stable that bridge designers may now consider using nonlinear time-history analysis for the seismic design of typical highway bridge structures.PUSHOVER ANALYSISMark R. Capron, he made a study on pushover based seismic evaluation of a 2,164 m long bridge located near the New Madrid Seismic Zone in southeastern Missouri. His research includes the existing structure, and the substructure retrofitted with column jackets, cap-beam modifications, and seismic isolation bearings. The research shows that the existing structure has 30% to 40% o f the displacement capacity required for the calciferol year design level, and significantly less than required for the 1,000 and 2,500 year levels that retrofits can improve performance to the 500 year level and that isolation bearings can improve performance of the main spans.Ima Muljati and Pennung Warnitchai, has studied the performance of Modal snap bean Analysis (MPA) in predicting the inelastic seismic response of multi-span concrete bridges. Considered bridge is subjected to lateral forces distributed proportionally over the span of the bridge in concurrence to the product of mass and displaced shape. Later the bridge is pushed up to the target displacement determined from the peak displacement of the nth mode inelastic single Degree of Freedom System derived from Uncoupled Modal Response History Analysis. Then the peak response from each mode is combined using Square-Root of Sum-of-Square (SRSS) rule. Results shows that the use of SRSS rule is not appropriate in this br idge and the displaced copy is shifted from the elastic shape due to yielding, Modal Pushover Analysis can predict well the total peak response of the bridge in inelastic range.P.S.Lande and A.D.Yawale, they studied that the structures within elastic range have tranquillize high displacement forces. Therefore it requires linear methods for analysis. He said that the bridge being a special type of structure requires higher(prenominal) load carrying capacity due to introduction of ductility in design requiring the design for lesser forces as compared to the forces obtained in elastic range. To evaluate the Non-linear behavior and sequential failure pattern in different components of the bridge, Pushover analysis is an effective tool. In his study, he deals with nonlinear pushover analysis at a specific bridge structure with elastic foundation in urban area. The procedure recommended in ATC 40 (Capacity Spectrum method) is adopted for analysis under various seismic demands. The hin ge formations for expected performance level are recorded. The response parameter like base shear roof displacement are studied. Performance point for bridge under consideration is determined.Jasmin A. Gadhiya and Anuj K. Chandiwala, has made a study on pushover analysis of bridge after 2001 Gujarat Earthquake and 2005 Kashmir Earthquake, and said that there is a nation-wide attention to the seismic vulnerability assessment of existing important structures. There are so many literatures available on the seismic evaluation procedures of multi-storeyed buildings using pushover analysis. Its known that bridge is a very important structure in any pastoral but there is no much effort available in literature for seismic evaluation of existing bridges. Bridges extends horizontally with its two ends restrained and that particular characteristic make the dynamic behavior of bridges different from building. Modal analysis of a 3D bridge model reveals that it has many closely spaced modes. P articipating mass ratio for the higher modes is very high. Therefore, pushover analysis with single load pattern may not yield correct results In order to address this problem, the aims of their study was to carry out a seismic evaluation case study for an existing RC bridge using nonlinear static (pushover) analysis and amphetamine curtail push over analysis and suggest whichever is better to understand bridge structural behavior. They considered a 12-span existing RC bridge for the case study. Standard pushover analysis using FEMA 356 (2000) displacement coefficient method and an upper bound pushover analysis method is used to analyses the bridge in which they have considered higher mode effects. And they concluded that evaluation results presented are shows that the selected bridge does not have the capacity to meet any of the desired performance level.