Experimental and numerical investigation on seismic performance of extended stiffened end-plate joints with reduced beam section using high strength steel

Abstract

The flexural behavior of bolted extended stiffened (ES) end-plate joints with high strength steel (HSS) is crucial in order to avoid brittle fractures in earthquakes. A total of three types of ES joints with different failure mode were carefully designed to cover commonly used types of joints, namely the full strength, equal strength, and partial strength joints. They were tested under cyclic loading to further investigate their seismic performance, and to evaluate the suitability of the design equations specified in European Code (EN 1993: 1-8 and EN 1998-1). Experimental results showed that the energy dissipation zone of the extended stiffened full (ESF) strength joints with HSS is mainly concentrated in the reduced section, while the one of the extended stiffened equal (ESE) strength joint using HSS is mainly distributed in the end-plate and the reduced section, both of them belong to ductile failure mode; the extended stiffened partial (ESP) strength joints with HSS only rely on the crack propagation and closure between the end-plate and the beam flange, and the limited plastic deformation of the end-plate to dissipate seismic energy, which presented brittle fracture; The failure mechanism and energy dissipation capacity of ES end-plate joints with HSS are closely related to the capacity design parameters αd, The capacity design calculation model of the ES joints based on the EN 1993: 1-8 code component method can accurately predict its failure mode, but the reasonable parameter αd needs to be further studied in European Code. Finite-element analysis was performed and showed good agreement with the experimental results. It was found that a higher likelihood of fracture in transition length rather than in the connection area was reconfirmed in both ESF and ESE joints, while for ESP joints, it is in the CJP weld of the beam flange end.