FREE-BODY BASED SOLVING STRATEGY FOR SEISMIC RESPONSES OF WEAKLY-COUPLED SYSTEM

The weakly-coupled system consists of a series of supporting structures interconnected by flexible connection components and is characterized by weak structural integrity and massive discrepancy between material damping of the supporting structure and connection component. Such two characteristics result in some limitations of the conventional seismic analysis methods using global vibration modes and proportional damping for the weakly-coupled system. In light of these, based on free-body analysis of the supporting structure and connection component, the equations of motion, which consider their inconsistent damping properties, were formulated in this study. To avoid potential errors brought by decoupling of the orthogonality conditions of global vibration modes, the equations of motion were solved in the frequency-domain. This method was validated by the shaking table test of an exampled weakly-coupled system, and the maximum errors of the top displacement with different input ground motions were between 1.2% and 5.8%. Moreover, comparisons between the present method and conventional modal superposition method proved that the usage of the global vibration modes and proportional damping can overestimate the coupling effect among supporting structures and cause larger systematic errors.