Seismic response of MRFs with partially-restrained bolted beam-to-column connections through FE analyses

Abstract

Even though partially-restrained (PR) bolted beam-to-column connection systems are not explicitly certified to be used for moment resistance in any current building specification, they represent a promising solution when included in modern steel moment resisting frames (MRFs), showing significant potential to mitigate some of the major drawbacks inherently related to welded connections. In order to quantify the influence of this attractive system on the global nonlinear dynamic response of whole MRF buildings subjected to seismic loads, a numerical procedure, based on detailed three-dimensional solid and one-dimensional fiber-based finite element (FE) models, has been developed and validated using past experimental results. High-definition FE analyses, accounting for material and geometric nonlinearities, as well as for the interaction among connection components via nonlinear contact algorithms, were able to capture stress/strain concentrations that faithfully reflect experimental observations. By contrast, the mechanical modeling approach discussed herein was applied to study these systems at a global scale. This simplified FE idealization has been used to assess the seismic performance of T-stub connection systems, within four- and eight-storey MRFs. These results were compared to those for other top-and-seat angle joints investigated in a past research program. A series of conventional and adaptive pushover analyses and incremental dynamic simulations have been carried out, using a suite of 44 records as seismic input, to quantify behavioral changes in the response of MRF systems as a function of geometric variations in the connection.