Study On The Seismic Performance Of The Prefabricated RCS Frame With Bolted Connection

The reinforced concrete column and steel beam(RCS)hybrid structure has the characteristics of low cost and high efficiency.It is a new type of assembly structure system which is economic and can give full play to the advantages of steel and concrete structure.The prefabricated RCS joint with bolted connection has the semi-rigid characteristics which is similar to the semi-rigid connections of steel structures,it has good ductility,energy dissipation capacity and can be repaired easily,these advantages make this kind of joints have a good engineering application prospect in seismic area.Based on the merits of RCS structure,prefabricated structure and semi-rigid joint,the prefabricated RCS joint with bolted connection is proposed in this paper.The joint consists of four parts: reinforced concrete column,steel beam,embedded parts,bolts and splice plates.In this paper,the quasi-static test of the proposed joint is firstly carried out and its seismic performance is studied.Based on the experimental study,the finite element software ABAQUS is used to simulate and analyze the parameters of the prefabricated RCS joint with bolted connection.The factors such as the friction coefficient at the connections,the pre-tightening force in the bolt and the overhanging length of the embedded part are studied respectively.Based on the parametric analysis,a method for calculating moment-rotation angle which is suitable for the connection of the prefabricated RCS joint with bolted connection is proposed and verified in open source software OpenSEES.According to the actual engineering conditions,three prefabricated RCS frames are designed.The static elasto-plastic analysis was carried out by using OpenSEES software and the results were compared with three rigid RCS frames and three bracing prefabricated RCS frames.Taking the 6-story frame as an example,the dynamic time-history analysis of the prefabricated RCS joints is performed.Modifying the initial stiffness of the prefabricated RCS joints to study on the impact of the initial stiffness on the seismic performance of the whole structure.In this paper,the main conclusions are as follows:1)The ductility and energy dissipation capability of the prefabricated RCS joints with bolted connection is better than the conventional rigid RCS joints.Compared with ordinary RCS frame,the lateral stiffness and yield strength of the prefabricated RCS frame are decreased,but the ductility of the prefabricated RCS structure is greatly improved.2)The comparison between ABAQUS numerical simulation and experiment shows that the FEM simulation results are in good agreement with the experimental results,which verifies the accuracy and feasibility of the ABAQUS model.The parametric analysis of the joint leads to the following conclusion: The change of the friction coefficient at the junction of the joints has no obvious effect on the trend of the load-displacement curve of the joints.As the friction coefficient increases by 0.1,the slip load at the joint connection increases by about 20%.With the increase of the pretightening force in the bolt at the joint,the initial slip load also increases,and gradually close to the end of the slip load,slip phase gradually tends to be flat;When the length of the embedded parts is too long,the extension of the embedded parts will yield ahead of the splice plates,so more attention should be paid in the actual design process,and the distance of the embedded parts should not be too long.3)Based on the parameter analysis of the new prefabricated RCS joints,the calculation method of moment-rotation angle which is suitable for this kind of joints is proposed.The simulation results in the OpenSEES software agree well with the experimental values,which shows that the proposed calculation method can better reflect the semi-rigid characteristics of the joints.4)The semi-rigid behavior of the prefabricated RCS joints has a significant effect on the mechanical performance of the joints.Reducing the initial stiffness at the connection of the joints has an obvious effect on increasing the structural period.The natural period of the structure increases with the decrease of the initial rotation stiffness of the connection.In practical engineering,by reducing the initial stiffness at the connections,the structure’s period can be effectively increased.5)As the initial stiffness of the prefabricated RCS joints changes,the structure’s weak layers change;In the same structure,the initial stiffness of the connection at the joint is not linear with the maximum inter-story drift angle of the structure,and a detailed study is required by the yield mechanism.Therefore,in the actual project,when the maximum inter-story displacement angle of prefabricated RCS structure does not meet the standard seismic requirements,strengthening the stiffness of joints has no effect to improve the problem,adding support to the prefabricated RCS structure can effectively improve the seismic performance of the structure.