Seismic analysis of coupled structural systems with nonproportional damping.
In analyzing seismic response of a sub-structure contained in a building or heavy-industry structure, the current industry practice is to first analyze the building subjected to the seismic ground motion, and then analyze the sub-structure using the response of the building floor where the sub-structure is attached to. Such uncoupled analysis approach ignores the interaction effect between the sub-structure and the building. This interaction effect has generally been assumed insignificant for cases in which the mass of the sub-structure is relatively small compared to the building. However, recent researches have revealed that under certain conditions, the interactions can be significant even for very light sub-structures. In order to account for such interaction effect, it is required to analyze the entire building including the sub- structure concurrently. Since the damping characteristics of the building and the sub-structure are different the damping matrix of the coupled structure is non- proportional.