Assessment of ASCE-7 Ground Motion Scaling Method Using Computer Model of Instrumented High-Rise Building

Performance-based earthquake engineering relies on accurate prediction of seismic demands from structural systems under given hazard conditions. In the past-decade, numerous approaches in predicting engineering demand parameters (EDPs) from structural systems were established. Some of these methods were implemented into the design guidelines and building codes. Among them, nonlinear static procedures (NSPs) have found a wide usage in practice for checking new designs and evaluating performance of existing structures. Today, there is a paradigm shift towards using nonlinear response history analysis (RHA) in lieu of NSPs to predict EDPs. The pre-requisite to nonlinear RHAs is a set of ground motions to be selected and scaled appropriately so that analyses results would be accurate (unbiased) and efficient (having relatively small dispersion). Considering that ground motions may show significant variability in frequency content and amplitude, small dispersion (variability) of EDPs is desired since it provides a confidence. There are currently many different methods in scaling and selecting records to be used in nonlinear RHAs. Since there are no experimental validation studies available up to date, the effectiveness of these methods can only be assessed using numerical simulations. These simulations require development of realistic computer models. In this respect, structural monitoring plays a key role in providing recorded motions on existing structures which can be used to create their well-calibrated (in terms of modal periods, damping etc.) computer modes. This paper shows how the recorded earthquake data from the 52-story high-rise building located in Los Angeles is utilized to create a realistic three-dimensional computer model. This model is also used to assess the accuracy and efficiency of the ASCE-7 ground motion scaling method in predicting the building's nonlinear response. It is concluded that the ASCE-7 method results in significantly high dispersion of EDPs despite the fact that median EDPs are well estimated.