Cyclic tests on improved beam-column connections

After the Northridge earthquake in 1994, some researches in USA have identified three critical issues that significantly affect the strength and ductility of beam-column connections: (i) fracture toughness of weld metal, (ii) geometry and size of weld access hole, and (iii) control of panel zone deformation. This paper reports the experimental results from the second phase of a major research program on ductility of welded beam column connections under cyclic loadings which is supported by the Natural Science Foundation of China. The experiments focus on the geometry and size of weld access hole. Three new types of connection details are proposed and eight full size specimens are tested under cyclic loading. The ductility, the stress concentration behaviour, and the hysteretic behavior of these connections are investigated. Moreover, the influence of connection details on both the ultimate strength and the premature fracture behaviour of these connections are also analyzed, formulating advices on improvement of connection details. The experimental results provide valuable information for updating the seismic design code of high-rise steel buildings in China.