Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/7548
Title: DETERMINATION OF DESIGN GROUND MOTION PARAMETERS FOR DISPLACEMENT-BASED DESIGN
Authors: Popatbhai, Panchal Amratbha
Keywords: EARTHQUAKE ENGINEERING;DESIGN GROUND MOTION PARAMETERS;DISPLACEMENT-BASED DESIGN;FORCE-BASED SEISMIC DESIGN
Issue Date: 2010
Abstract: In traditional force-based seismic design of structures an equivalent seismic base shear is calculated based on the estimated fundamental period of the structure and an elastic response spectrum that is representative of the seismicity of the site. The design base shear value depends on the period of the structure, location and importance of the structure as well as on the nature of foundation soil. The inelastic inter story drifts produced by the design forces are obtained from the calculated elastic drifts and checked against codal displacement limits. In performance based design the performance of the structure during earthquake is a function of the ductility demand placed on structure and displacement induced in structure. Displacement based design methods are better able to ensure a uniform level of performance and therefore attracted considerable attention during recent year. Acceleration design spectrum representing seismicity of the site is primary input required for force based seismic design. Similarly, accurate displacement spectra are essential input of displacement based design. In current seismic codes the base shear force is prescribed in terms of elastic design spectra. However, the structure will undergo inelastic deformation under strong seismic events. Such inelastic behaviour is usually incorporated into the design by dividing the elastic spectra by a response reduction factor. Response reduction factor reduces the spectrum from its original elastic demand level to a design level. If accurate inelastic response spectra are available, seismic demand can be directly obtained using these spectra. In the present study attenuation relationship for inelastic displacement spectra has been developed for Indian regions. A review has been carried out to study the design spectra given in different National Codes for design namely Eurocode, New Zealand code and Indian code. Effect of all parameters associated with displacement response spectrum such as earthquake magnitude, local geological condition of site, source to site distance and low-frequency content present in acceleration time history etc. has been studied. The parameters of low and high pass filters and their effect on the response spectra has been critically reviewed. The attenuation relationship based on elastic and inelastic response spectra given by various researchers has also been reviewed. The attenuation relationship for the geometric mean horizontal elastic as well as inelastic constant ductility displacement spectra using Indian strong motion data set and some selective NGA (Next Generation Attenuation Project) data set has been proposed for Indian regions. The proposed empirical equation includes a consideration of moment magnitude, closest horizontal distance to the surface projection of the fault rupture, site category (rock/soil) and fault mechanism (strike-slip/reverse). Due to lack of data from Himalayan region for present study additional strong-motion data from NGA data set have been included. A set of 163 records from 16 earthquakes with moment magnitude ranging from 5 to 7 and Joyner Boore distance (RJB) distance ranging from 0-180 km have been used. Approximate solution for nonlinear response of yielding structures based on equivalent elastic system has gained a wide interest. Various techniques are available to consider nonlinear response of inelastic system into equivalent elastic system and simplifying the structural design procedures, such as equivalent damping procedure and constant ductility method. In the present study basis spectra the inelastic response spectra proposed by Chopra (2007), inelastic response spectra developed by using equivalent damping procedure and inelastic response spectra obtained from attenuation relationship given by Campbell and Bozorgnia (2010) have been compared using elastic response spectra for Eurocode, New Zealand Code and Indian Code as for constant ductility spectra. From comparison of inelastic design developed by using various methods, it has been found that yield acceleration response spectral ordinates determined by Chopra's methods are lower than same yield acceleration response ordinates determined by equivalent damping procedure. The comparison of inelastic spectra shows that the yield acceleration spectral ordinates obtained by attenuation relationship given by Campbell and Bozorgnia (2010) is quite lower than yield acceleration spectral ordinates determined by Chopra's (2007) constant ductility methods and equivalent damping procedure. It has been also found that variation in displacement ordinates for μ=2, μ=4 and j=6 determined from attenuation relationship are small. While variation in displacement ordinates determined by equivalent damping procedures for same ductility factors are large.
URI: http://hdl.handle.net/123456789/7548
Other Identifiers: M.Tech
Research Supervisor/ Guide: Singh, Yogendra
Shaema, M. L.
metadata.dc.type: M.Tech Dessertation
Appears in Collections:MASTERS' THESES (Earthquake Engg)

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