Evaluation of the seismic level of protection of steel moment resisting frame building structures

A large number of low and medium-rise buildings have steel moment resisting frames as the primary lateral load resisting system. During the past few decades, much confidence has been placed on this type of structural system for resisting seismic loads. However, after recent earthquakes (e.g. Northridge, California, in 1994, and Kobe, Japan, in 1995) the confidence in this system was reduced as a result of various types of damage that moment resisting steel frames have suffered. This resulted in a recognition of the need to evaluate the performance criteria on which current provisions are based.; The main objectives of this research study are: (i) to evaluate the seismic level of protection afforded to steel moment resisting frame building structures designed in accordance with the current Canadian provisions (i.e. NBCC (1995) and CAN/CSA-S 16.1--94), and (ii) to investigate the effect of the different design philosophies and seismic hazard design levels on the inelastic dynamic response of multi-storey steel frame structures.; In the study analytical models are modified and incorporated into the PC-ANSR computer program in order to perform the inelastic dynamic analyses of the frames. The inelastic models take into account the spreading of inelastic deformations in beam-column elements, connection flexibility and panel zone deformations. A cyclic model for the panel zone element is developed and introduced into PC-ANSR. The performance of the frames is evaluated both statically using monotonically increasing lateral load (nonlinear push over static analyses), and dynamically by subjecting the inelastic model to an ensemble of actual strong ground motion records (time-history analyses).; The main ensemble of time-histories used in the study consists of twelve earthquake ground motion records selected on the basis of Newmark-Hall design spectra amplification factors. An additional ensemble of time-histories (twelve records) is selected based on the uniform hazard spectrum for Vancouver which describes the new seismic hazard information given by the Geological Survey of Canada.; The results of the inelastic dynamic analyses are presented in terms of statistical measures of the maximum response parameters determined during the time-history analyses. Also, the results of the nonlinear push over analyses are presented and compared with those of the dynamic analyses. The performance expectations of the frames are evaluated in order to assess both the overall level of protection provided to the frames and the preferred design philosophy. (Abstract shortened by UMI.)...