Response Spectra of Strain Hardening Structural Systems to Earthquake Motions

The effect of strain hardening in limiting the forces developed in structures subjected to earthquake motions below those of the elastic behavior is investigated by treating a single degree of freedom system. Response spectra for El Centro earthquake, May 1940 are generated from an idealized bilinear strain hardening resisting force-displacement relation for different values of the strain hardening coefficient and ductility factor. Optimum response spectra are presented in terms of the yield displacements and the maximum displacements. For a system with the optimum yield displacement, the maximum displacement response is always less than that of the elastic system, and thus the optimum response spectra may be used as a guide in selecting members for a displacement constrained design.