Q-FACTOR VERIFICATION OF A 6-STOREY CONCENTRICALLY BRACED FRAME VIA THE INNOSEIS RISK-BASED APPROACH

A case study example is presented to support a methodology that evaluates the design behaviour-factor on a risk-basis, using the code-compatible performance targets for life safety and global collapse.The case study employs a 6-storey concentrically braced frame with a detailed physics-based representation of braces.Nonlinear static analysis is conducted to provide an estimate of overstrength and an approximation of the behaviour-factor.Incremental Dynamic Analysis is subsequently performed to obtain a refined representation of response throughout the desired range of seismic intensity.Besides the widely-adopted first-mode spectral acceleration, state-of-the-art intensity measures such as the so-called average spectral acceleration, are used to illustrate the severity of the ground motions considered.The dynamic analysis results for the considered modes of failure are conveniently summarised into fragility functions, which are further convoluted with the seismic hazard function in order to derive the associated mean annual frequency of exceedance.A comparison among the derived and the allowable mean annual frequencies determines the applicability of the behaviour factor for the structure examined, showing that EN1998-compatible factors may accurately be evaluated.