Behavior of two-storey welded steel frames strengthened with external prestressed strands

Abstract

A possible solution for enhancing the resistance of welded steel frames against progressive collapse is external installation of prestressed strands. Although several experimental studies have been conducted on steel frames with prestressed strands, most of these studies have focused only on individual joints or single-story substructures, while neglecting the interaction between different stories in multi-story frames. The objective of this research is to conduct a detailed study on the impact of prestressed strands on the progressive collapse resistance of welded steel frame structures. Pushdown tests were performed on two-story steel frame substructures with and without prestressed strand strengthening. Additionally, corresponding numerical models were established using LS-DYNA. Further parametric analyses were conducted to investigate the effects of prestressing level, strand diameter, layout type, and lateral restraint stiffness on the collapse resistance. The results show that the load-carrying capacity of frames strengthened with prestressed strands is higher than that of bare steel frames, which is mainly attributed to the significant enhancement of the frame's catenary action (CA) capacity after prestressed strand strengthening. Furthermore, analysis of horizontal reaction forces indicates that there are differences in the CA resistance among different stories. Through numerical analyses, it is concluded that compared with polyline and diagonal layouts, the straight and parallel layout provide a more significant enhancement in the load resistance of steel frames