Seismic behavior investigation of TOB bolted endplate connection with novel internal strengthening structure

Abstract

This paper presents the results of the cyclic loading test on Thread-fixed One-side Bolts bolted Endplate Connection (TOBEC). Two types of novel strengthening structures including double H-shape stiffener and polygonal steel tube stiffener were applied to the connection to increase the length of the threads and improve the bending strength of the Hollow Square Column (HSC). Six full-scale specimens in total were designed to study the effect of the thickness of the strengthening structure sidewall/flange, and the thickness of the endplate on connection seismic performance. The failure modes, bending moment-rotation relationship, and the seismic performance of each specimen were analyzed and evaluated. Test results revealed that the strengthening structures could significantly improve connection mechanical performance. Meanwhile, the unwanted failure mode of hole thread failure and the column wall yielding failure could be avoided by utilizing strengthening structures moderately. Moreover, limited experimental results indicated that the double H-shaped stiffener was more effective in increasing the bending strength of the column wall. The strengthened connection could display satisfactory seismic performance in terms of rotation capacity, strength degradation, stiffness degradation, and energy dissipation.