EARTHQUAKE GROUND MOTIONS AS THE INPUT OF NONLINEAR TIME-HISTORY ANALYSIS ACCURACY AND LEGITIMACY

Abstract eng:
Today, Nonlinear Time-History Analysis (NLTHA) is one of the key methods to estimate the dynamic response of engineering structures with adequate accuracy. Particularly, in the case of critical or special structures, irregular systems and tall buildings, NLTHA can be the best choice to compute the Engineering Demand Parameters (EDPs). Most of the existing seismic standards provide the designers with a reduction in the conservatism when they select more complicated analysis types such as NLTHA. Also, new generation of seismic guidelines confirm the method as an efficient tool in performance based earthquake engineering. For building structures under seismic loads, unlike the dynamic excitation of mechanical systems, the non-stationary nature of earthquake ground motion can affect and even control the dynamic behavior of systems. Therefore, the essential step in NLTHA is to select a set of ground motions in order to achieve a reliable estimation of desired EDPs. The existing methods suggest the selection, scaling, matching and artificial generation of Strong Ground Motion Records (SGMRs) to ensure the compatibility with the design intensity levels. There is a variety of proposed methods in the earthquake engineering literature focusing on the importance of input SGMs in NLTHA, while some controversial issues such as the selection and scaling of vertical components, selection of a horizontal pair of components in case of bidirectional analysis, near-fault characteristics and the influence of the higher modes of vibration are still unresolved. In this paper, pros and cons of the application of ground motion preparation methods for NLTHA have been studied. After a comparison among the features of most common approaches, the influence of methods on the dynamic response of nonlinear systems is examined.

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