Multi Support Excitation of Steel I Girder Bridge Under Spatially Varied Earthquake Ground Motion

Abstract

Response of steel I girder bridge subjected to spatially varied ground motions is examined through response spectrum and time history analysis. It is easy to predict or calculate the response of small base structures like buildings under spatially varied ground motions because the excitations caused by earthquake is considered to be same at all supports . But for extended areas like long span bridge structure is one of challenge for engineers to investigate the response and dynamic behavior under the effect of spatially varied ground motions The spatially varied ground motions implemented in the structure are due to three causes; a) wave passage effect i.e. difference in arrival of wave or time lag effect at different supports .b) loss of coherency i.e. difference in amplitudes of waves due to different medium of ground c) local site conditions i.e. the type of soil (soft, firm, hard). Simulation of ground motions with different efficient algorithms and computer code (using MATLAB) were generated in the form of time period and acceleration. Kanai –Tajimi model is used for simulation of ground time history analysis. Using actual earthquake record data with different magnitude and frequencies for evaluating the model for time history analysis is done. Moments and shear force for different loading, response spectrum and time history analysis for different ground motions is calculated. It is concluded that the moments and shear force considering wave passage effect, loss of coherency and local site conditions are much higher than others.