Response of self-strained structures to multiple time-phased seismic excitation

The response of structural systems to seismic excitation is affected by the presence of axial forces in the members as well as by the time-delayed arrival of the seismic wave at the various excitation points. The natural frequencies and other dynamic properties are influenced by the presence of axial forces. As a result, the response of the structure changes to the extent that the axial forces change its dynamic characteristics and to the extent that these characteristics are relevant in the interaction of the structure with a given earthquake. This paper presents a parametric study of some simple structures whose numbers are subjected to initial axial forces and to the action of multiple time-phased seismic motion of the supports. The final response is obtained by superposition of instantaneous values of modal contributions, after numerical integration of the modal equations. The disturbing action produced by the ground motion of the well-known El Centro earthquake 1940 is appled to several simple structures in which the amount of the axial straining forces and the time-delayed excitation are varied parametrically. (Auth.)