Strategies for Identifying Critical Seismic Response Combinations

The effects of multiple seismic responses acting simultaneously within a structural element must often be considered when checking the capacity of the element or determining its required dimensions or material properties. In particular, an element is viewed as being adequately designed if all combinations of the responses as they evolve during an earthquake remain in the safe region of the response space defined by the relevant capacity surface of the element. In this paper, algorithms are developed to facilitate the comparison of available response-spectrum-based envelopes to prescribed capacity surfaces for the purpose of either assessing the adequacy of an existing design of a structural element or determining the required value of a design parameter. Comprehensive examples are used to demonstrate the implementation, interpretation, and utility of the proposed algorithms.