Seismic performance of thread-fixed one-side bolts bolted extended endplate connection to HSST column with internal strengthening components

Abstract

This paper presents experimental results of the seismic performance of the Thread-fixed One-side Bolts bolted Endplate Connection to Hollow Square Steel Tube column (TOBEC-HSST) with internal strengthening components. Five specimens were tested under cyclic loading. The main variable parameters affecting the seismic behavior of specimens were the internal strengthening structure types (i.e. the polygonal steel tube without inner stiffener, or with the horizontal or vertical stiffener) and the extended endplate types (i.e. with or without the endplate stiffeners). The failure modes of connections were observed, the moment-rotation hysteretic response and the strain distribution of connections were obtained. Besides, the rotation ability and ductility, the degradation of strength and rigidity, and the energy dissipation capacity were analyzed and compared, which were affected by the strengthening measures. The introduction of the endplate stiffeners can improve the overall rigidity of the joint region and sufficiently develop the energy dissipation capacity and ductility of the connections, and the contribution from the inner stiffener in the internal strengthening polygonal steel tube can also enhance the seismic performance of the connections. In addition, the rotations at the failure of the connection were larger than 30 mrad, which satisfied the ductility limitation requirement in reference to FEMA-350, revealing a potential to the application in seismic steel structures.