Seismic behavior of inter-module bolted connections with reinforcement for modular steel buildings
Module-to-module steel connections are susceptible to the module's beam-column weld tearing under seismic action,significantly weakening the connection's seismic performance.To protect the beam-column weld,two strengthening methods,diagonal brace and flange strengthening,were proposed to enhance the seismic performance of the connections.To study the effects of different strengthening methods(diagonal brace strengthening,flange strengthening),bolt-hole types(circular bolt hole,dual-slot hole),connection types(comer connection,side connection),and loading methods(monotonic loading,cyclic loading)on the seismic behavior of the connections,ten full-scale connections were tested and the results were discussed in this paper.Moreover,the force-deformation characteristics,bearing capacities,rotational stiffness,ductility,and other seismic performance indexes of the connections were analyzed.An elaborated finite element model was developed and validated by the test results.Then,numerical simulations of key parameters were conducted for comparative analysis.The findings indicate that the beam-column welds in the modules of the reinforced connections exhibit negligible instances of weld tearing.The main deformation characteristics of the specimen are bending deformation and local buckling of the beam,weld tearing at the reinforcement and flange fracture.Connection stiffness properties are classified as semi-rigid.Both diagonal brace strengthening and flange strengthening connections exhibit favorable energy dissipation capacity,diagonal brace strengthening connections have higher load-carrying capacity and stiffness,but their ductility is lower than that of flange strengthening connections.The use of slotted holes hardly affects the seismic behavior of the connections.The rotational capacity and ductility of the corner and middle connections are essentially the same.Under cyclic loading,the ductility of diagonal brace and flange strengthening connections decreased by about 39.2％and 53.5％,respectively,compared with that of monotonic loading,but still meets the connection ductility requirements in the code for seismic design of buildings GB 50011-2010.Within the range of parameters set in the numerical simulation,the variation of the thickness of the diagonal braces has a small effect on the bearing capacity of the connections,but it increases with the increase of the welding distance of the diagonal braces.Adjusting the length of the reinforcing plate improves the load-carrying performance of the connection after reaching the yielding moment.
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