Seismic Analysis using Inelastic Constant Ductility Response Spectra for Performance Based Plastic Design of Steel Moment Resisting Frame

Performance Based Plastic Design (PBPD) method overcomes implicit consideration of inelastic behavior of structural system designed by existing force/strength based approach. The effectiveness of PBPD for various Lateral Load Resisting Systems (LLRS) is ascertained through research in the past decade. However, the validated PBPD designs of these LLRS are still based on elastic design spectra which lead to a conservative estimate of seismic demands. Hence, there is need to develop the inelastic constant ductility response spectra for such structural systems. This paper aims to propose use of inelastic constant ductility response spectra for PBPD of Steel Moment Resisting Frame (SMRF). 20 Large Magnitude Small Radial -distance (LMSR) ground motion records are used to develop these inelastic constant ductility response spectra for various PBPD cases of 3 and 9-storey SAC-steel project buildings. The seismic performance of these PBPD cases using both inelastic constant ductility response spectra, as well as elastic design spectra, are evaluated by carrying out Nonlinear Static Pushover Analysis (NSPA) and Nonlinear Time History Analysis (NTHA). The results show that PBPD cases using inelastic constant ductility response spectra are more efficient and effective in achieving the target ductility and pre-selected yield mechanism as the performance objectives over elastic design spectra.