Dynamic Substructuring for Alternating Subsystems

A method of analysis is developed for determining transient responses of large structural systems subject to changes of structural components. A dynamic structural system is divided into two subsystems: the support that remains unaltered and is subject to external excitations, and the branch that is liable to change and on which external excitations may be acting. A distinctive feature of the method is the use of specified sets of generalized modal displacement functions or mode shapes for each subsystem. This enables incorporation of the modal properties of the alternative subsystem without having to re-establish the entire system modal properties in each new analysis. The method is applied to a 16-story building rigid frame model. The method gives transient response results comparable with the conventional integrated system analysis. Approximations due to modal truncation are the same as component-mode substitution method.