INVESTIGATION ON DIFFERENT LATERAL EARTHQUAKE FORCE METHODS OF ANALYSIS

Abstract

In the concept of lateral seismic design there are three famous analysis methods. These methods include the equivalent static load (ESL), modal response spectrum (MRS) and time history analysis (THA). In this study, the variation in the resulted base shear using any of these methods is investigated. The modal response spectrum analysis, either simplified (same as ESL) or multiple, is carried out using the elastic design spectrum specified by the renewed Egyptian Code of Loads (2008 ECOL). The time history analysis is applied using seven delibrate different real earthquake excitations selected to match the specified elastic spectrum and soil type. Suggestions to rationally enhance the seismic protection level obtained from the multiple response spectrum is presented and emphasized. This study extends to analyze and compare our resulted base shear with those obtained from different international codes as the European, American and Canadian codes for sites with similar conditions. Special emphasis is paid to evaluate the ECOL response modification factors compared with the considered codes. It is found that there is high variation between the base shear obtained using the code specified different analysis methods and in comparison with the considered codes and hence some seismic provisions in the new 2008 ECOL need to be recontemplated.