Experimental evaluation of inelastic dynamic amplification factors for progressive collapse analysis under sudden support loss

Abstract

A small-scale test setup is devised to investigate the inelastic dynamic amplification factors (DAFs) for structures subjected to sudden support loss. Based on three different definitions, experimental DAFs are calculated from static and dynamic support-release tests. Comparison results indicate that DAFs obtained from the neutral displacement response cannot account for the inelastic dynamic effect on either the displacement or force response. The displacement-based DAFs are apparently different from the force-based DAFs in the inelastic range. The former is larger than 2.0 and exhibits a concave downward variation with displacement ductility. On the contrary, the latter is less than 2.0 and exhibits a concave upward variation. Both of them may asymptotically return to the elastic DAF under large deformation as the specimen presents significant strain-hardening behavior. Pseudo-static response analysis is carried out for prediction of inelastic DAFs using the load–displacement curve obtained from the nonlinear static test. Also, analytical formulae with consideration of post-yield stiffness ratios are derived from the pseudo-static response analysis. They are proved to be capable of simulating the variation of inelastic DAFs with ductility demand.