Study On Comparison Of Seismic Response Analysis Methods For Soft Soil Sites

A large number of earthquake damage investigations and studies have shown that the soft site conditions have an important impact on ground motion.Currently the equivalent linearization method which commonly used in engineering cannot solve the large deformation and strong nonlinear characteristics of soft soil under strong earthquakes.The results of the seismic response analysis of the stratum are obviously contrary to conventional understanding,so it brings potential risks and great uncertainty to the seismic protection of the project in the area covered by the weak field.In view of this,a comparative study was conducted around several currently accepted seismic response analysis methods(LSSRLI-1,SHAKE91,SOILQUAKE,and NERA),using the vertical arrays of the weak and strong site conditions in the Japanese strong seismic network KiK-net,uphole and downhole Strong earthquake observation records to verify the feasibility and applicability of several analysis methods on the ground effect of weak ground motions.By comparing the typical ground motion parameter results(peak acceleration,response spectrum,etc.),summarizing the various methods in different site category conditions Under the difference and deviation degree,a seismic response analysis method for the soft site conditions suitable for the project was finally determined.The main work and preliminary achievements of this article can be outlined::(1)Collected several typical seismic response analysis programs at home and abroad,including equivalent linearization and nonlinear analysis methods,and analyzed their calculation principles and differences,intending to analyze the reasons for the difference in calculation results.(2)According to the site classification standard of China's "Code for Seismic Design of Buildings" GB50011-2010,332 measured records on 24 weak site stations were collected from the KiK-net strong earthquake network in Japan.Through the statistical analysis of the measured records,the amplification effect of the weak ground under the action of different strength ground motions is preliminarily understood,and the estimated value of the amplification coefficient of the soft soil site is given(2.7).(3)Based on typical kind of sites(???????),selecting strong vibration input for seismic response analysis,and compare the calculated values of the ground motion parameters(site amplification factor,response spectrum)with the measured values to preliminary analyze each earthquake According to the reliability and adaptability of the reaction program,preliminary analysis believes that SOILQUAKE,the equivalent linearization method based on frequency correlation,performs best in various venues.(4)Ten soft sites of category III and IV were selected,and a total of 28 working conditions were analyzed for seismic response.The results show that the calculation results of SOILQUAKE and SHAKE91 are closer to the measured value,with an average deviation of about 30%,but in response spectrum,SOILQUAKE is closer to the actual measurement;the site amplification factor calculated by LSSRLI-1 and NERA is generally smaller than the measured value,and the average deviation is close to 50%.Considering comprehensively,the calculation result of the equivalent linearization program SOILQUAKE based on frequency correlation is more reliable under the action of weak ground and strong vibration.