Implementation of modal combination rules for response spectrum analysis using GEMINI

One of the widely used methodologies for describing the behavior of a structural system subjected to seismic excitation is response spectrum modal dynamic analysis. Several modal combination rules are proposed in the literature to combine the responses of individual modes in a response spectrum dynamic analysis. In particular, these modal combination rules are used to estimate the representative maximum value of a particular response of interest for design purposes. Furthermore, these combination rules also provide guidelines for combining the representative maximum values of the response obtained for each of the three orthogonal spatial components of an earthquake. This report mainly focuses on the implementation of different modal combination rules into GEMINI [I]