Seismic performance of H-shaped steel beam-to-square steel corner column connection with external strengthened ring

Beam-to-column connection plays a key role in structure designs, especially for steel structures, as the seismic performance the connection directly affects the safety, reliability, utilization, and economic indicators of steel structures. During the Northbridge earthquake in the USA and Hyogoken Nanbu (Kobe) earthquake in Japan, several steel structures collapsed because of unexpected brittle fractures around the beam-to-column connections. The economic loss encountered in the Kobe earthquake is estimated to be about 10 trillion JPY (approximately 580 billion RMB). Moreover, it caused approximately 6500 civilian fatalities and destroyed tens of thousands of houses in Kobe and the surrounding cities. The corner beam-to-column connection suffered from complicated seismic loadings during the earthquakes. Corner beam-to-column connections are the weak points in an aseismic design, and under biaxial lateral loadings, they induce large torsional deformations. In this study, five specimens were tested under pseudo-static loadings to investigate the influence of loading paths on the seismic behavior of corner or side beam-to-column connections. The main experimental parameters were the loading paths (uniaxial loading, biaxial symmetrical loading, and biaxial center symmetrical loading) and width-to-thickness ratio of the steel column (D/t=22 and 33). The main seismic characteristics of specimens were studied, such as the hysteretic behavior, stiffness degradation, and energy dissipation. The results indicate that the loading paths affect the stiffness and bearing capacities of the specimens. The bearing capacities of the specimens under the biaxial center symmetrical loading are 20% lower than those under the uniaxial loading, while the bearing capacities of the specimens under the biaxial symmetrical loading are equal to those under the uniaxial loading. The width-to-thickness ratio of the square steel column is one of the key factors that affect the bearing capacities of the specimens. The bearing capacities gradually decrease with an increase in the width-to-thickness ratio. All the specimens exhibit a good energy dissipation capacity, and the hysteretic curves are stable and numerous. The equivalent viscous damping coefficients of all the specimens are around 0.2.