Evaluation of structural response and damage resulting from earthquake ground motion

The design of structures to limit or preclude strong response and damage from earthquake ground motion is a complex problem and is the subject of this thesis. The factors leading to strong response are not well understood and clearly involve more than peak acceleration and yield level. Present methods for evaluation of damage are approximate, generally focusing on the maximum ductility. This study was undertaken to identify the parameters responsible for strong response and to develop comprehensive new approaches for evaluating damage in simple structures.;The initial studies reported herein involve the response of various single-degree-of-freedom (SDOF) elastoplastic structures to pulse-type ground excitation and to actual earthquake ground motion; among the results documented are structural deformation response, input and hysteretic energies and number of yield excursions. Also included are the results of a limited Fast Fourier Transform study and experimental investigation of a SDOF structure subjected to pulse-type excitation.;The second set of studies reported involves development of two comprehensive seismic damage criteria. One criterion converts the dissipated hysteretic energy into an equivalent number of identical hysteretic cycles employing three different cycle definitions. The second damage criterion accounts for the accumulation of structural damage caused by random inelastic cyclic response through hysteretic plastic ductility and Damage Index parameters founded on low-cycle fatigue concepts. These damage criteria are evaluated against experimental data and found to depict damage well.;Three applications of these damage criteria are presented, namely (a) evaluation of the dissipated hysteretic energy using equivalent cycle and fatigue damage concepts, (b) use of the fatigue damage criterion to construct inelastic response spectra, and (c) use of the fatigue damage criterion as the basis for a proposed drift criterion to limit the damage caused by cyclic response.;The study concludes with observations regarding the contribution of the various ground motion and structural parameters to strong response, performance of the proposed damage criteria, and the impact of this investigation on current design philosophy.