| The research focuses on accurately predicting the general higher-mode effect (HME) responses and performance objectives of structures excited under various ground motion inputs. Unlike time-history analyses that use time-consuming procedures to predict the structural response over time intervals, the general pushover provides a much simpler insight into the seismic demands as incurred through ground motion input. As there currently exists a need to establish rational, accurate, and simplified seismic and nonlinear analysis methods, research in nonlinear pushover analysis has been extremely active in recent years and has only recently been investigated for implementation into a design office setting.; Improving upon other commonly used pushover procedures, which do not have the capability of predicting higher-mode effects (HMEs), a new pushover approach is used with similar simplicity and ease of implementation to accurately define the resulting performance objectives. Based on fundamental, elastic structural dynamics theory, a variant inertial force distribution is developed at each state of post-elastic activity and is used to push the multi-degree of freedom (MDOF) structure to failure, thus defining the structure's capacity curve. By updating the structural characteristics along the push, the model is able to adjust to the behavior of the structure as opposed to forcing the structure to respond according to the model while retaining the degree of accuracy through the accountability of the HMEs. The pushover uses the energy contribution of several fundamental mode shapes in a weighted sense to provide an overall flexibility of inertial force redistribution through the structural characteristic updates leading towards the ultimate target displacement prediction. Using an optimization procedure to minimize the response error, specific capacity and demand parameters of the pushover analysis are determined and are used to combine a number of first modes in an elastic and inelastic sense; using these modes, a representative single-degree of freedom (SDOF) bilinear relationship is defined. Examination of several structures under varying ground inputs in this perspective allows an overall characterization of the structural responses to be made through the optimal parameter identification. The final targeted displacement predictions are shown to conform well to those as determined by a nonlinear time history analysis. |
