Seismic behaviour of TSOBs bolted I-beam to hollow section square column connection with inner stiffener

Four T-head Square-neck One-side Bolts (TSOBs) bolted I-beam to Hollow Section Square Column (HSSC) connections with H-steel stiffener were tested under cyclic load, where the key parameters were the length and plate thickness of the H-steel stiffener. The seismic performance of the test connections is evaluated by comparing with that of the unstrengthened joint. The test results show that: (1) The ultimate rotation of the strengthened connections is more than 30 mrad, which is required by the US seismic code FEMA-350; (2) The H-steel stiffener changes the connections from partial strength to full strength, but do not change the semi-rigid characteristic; (3) The H steel stiffener retards the stiffness degradation and strength degradation, and thickening and extending stiffener can get better results; (4) The H-steel stiffener can increase the energy dissipation of the connections by 63.2% on average, and 102.3% on maximum. In the design of strengthened connections, H-steel stiffener, especially extended H-steel stiffener is recommended. In addition, controlling the size of the assembly gap between the HSSCs and the H-steel stiffener, adding anti-slip bolts, and setting mortise and tenon splice are recommended to reduce the slip displacement between the HSSCs based on the finite element analysis results. Eventually, the method and models for predicting the yield bending moment of the connections are proposed in this paper. The calculated results agree well with the tested ones and have a certain degree of safety reserve.

Automated summary

This study investigates the seismic performance of connections strengthened with H-steel stiffener, showing that H-steel stiffener can improve the ultimate rotation and energy dissipation of the connections. Design recommendations include the use of H-steel stiffener, especially extended ones, and measures to reduce slip displacement.