Recent Experimental Research Advances on the Seismic Performance of Joints in Multi-storey and High-rise Steel Structures

The steel Moment-Resisting Frame has been widely used in multi-storey and high-rise constructions, as it has many advantages over common structures, such as better aesthetics, better seismic performances with less weight and easy assemblage, etc. In the Northridge earthquake (1994) and the Kobe earthquake (1995), widespread and unpredicted brittle fractures were. found in welded steel beam-column connections. Research on seismic behaviors of beam-column connections became a worldwide research spot. This paper introduces the main research results on steel beam-column connections of the Research Section of Steel Structures and Glass Buildings of Tsinghua University during the last decade, including experimental studies and design suggestions on pure steel beam-column joints and composite joints. (1) In this paper, a series of 8 specimens containing 4types of connections such as dog-bone type, long slot type and enlarged-access-hole connections were tested by cyclic loads. The affects of the connection details were analyzed, and the seismic behaviors of these joints were studied based on tests. (2) In this paper, 8 Welded-Flange-Bolted-Web (WFBW) specimens with 4 types of access holes were tested by cyclic loads. The seismic behaviors of connections and the influences of access holes were analyzed, and some structural requirements were proposed. (3) A test of 4 composite joints with different access holes and reinforcement ratios under cyclic loading was conducted to investigate the moment resistances and seismic behaviors of composite joints. The failure modes and ductility characters of these specimens were concluded and the test results were compared with pure steel connections. The connection stiffness degradation and the energy dissipation capacity were also discussed. At last the design suggestion of the composite joints was proposed. (4) Another test of four composite joints with different reinforcement ratios and loading types was conducted in this paper. This test focused on the affects of material and loading types. Generally, these tests and the design theories provide an in-depth sight into the studies and design methodologies of the steel and composite connections. It will promote the use of the steel structures and composite structures in our nation.