APPLICATION AND IMPROVEMENT OF DIRECT SOLVING METHOD IN SEISMIC RESPONSE ANALYSIS OF STRUCTURES UNDER MULTI-SUPPORT EXCITATIONS

The direct solving method, in which absolute displacement is utilized to solve dynamic equations, is proposed to analyze the seismic response of structures under multi-support excitations. Compared with the commonly used decomposition method, which decomposes the displacement into absolute pseudo-static displacement and relative dynamic displacement, the direct solving method is of a more concise concept as well as lower calculation complexity. And it is more suitable for nonlinear problems. As for the direct solving method combined with mode superposition method, calculation with only low order modes may cause large error. Thus static correction method is adopted to improve the precision of direct solving method. Results of numerical examples indicate that sufficient accuracy could be gained with fewer low order modes by using modified direct method. And it is also concluded that the precision of modified direct method is similar to that of decomposition method.