Study On Seismic Fragility Of RCS Structures With Asymmetric Friction

The assembled reinforced concrete column(Reinforced Concrete Column)-steel beam(Steel Beam)composite frame structure(RCS composite frame structure)fully combines the advantages of steel and concrete materials and has been widely used in engineering construction in recent years.At present,the research on the seismic performance of the assembled RCS structure is mainly based on the yielding energy consumption of the structure itself,while the research on the assembled structure with energy dissipation and damping technology is relatively limited.Based on this,the group proposes a new type of RCS beamcolumn splice node with asymmetric friction connection(AFC),which sets the asymmetric friction connection at the splice of the lower flange of the pre-built steel beam and the loaded steel beam to improve the seismic performance of the node by using the frictional energy dissipation of the asymmetric friction connection.In order to study the seismic performance of RCS beam-column nodes with asymmetric friction connections,three groups of RCS beam-column nodes with AFC connections were subjected to reciprocal loading tests considering the structural factors such as bolt preload and friction shim material.The test results show that:(1)the damage form of the three groups of specimens is beam hinge mechanism damage,and the plastic hinge occurs at the steel beam splice,which meets the seismic design requirement of "strong node,weak member";(2)the hysteresis curves of the three groups of specimens are full and stable,with obvious double platform energy dissipation,which is conducive to the realization of the two-stage seismic prevention target;(3)the use of wear-resistant steel as shims is different from the use of friction shims.wear-resistant steel as shims,and the two groups of specimens using brass as shims,the bearing capacity and hysteresis curves are similar,and have better energy dissipation performance;(4)Increasing the bolt preload can improve the bearing capacity and energy dissipation capacity of the specimens.Based on the experiments,the nodes of RCS beams and columns with AFC connections are numerically modeled in Open Sees using nonlinear zero-length cells with Pinching4 material.The comparison of the simulation results with the experimental results shows that the established node model can well simulate the frictional slip behavior of the nodes during repeated loading,which verifies the validity of the node model.In order to investigate the effect of the nodes with asymmetric friction dissipation on the seismic performance of the overall frame structure,a model of RCS frame with asymmetric friction connection and normal node RCS frame is established in Open Sees based on the incremental dynamic analysis(IDA)method,and the susceptibility analysis is performed.The results show that in the case of small earthquakes,the transcendence probability of the RCS frame with asymmetric friction connection reaching the limit state is similar to that of the ordinary nodal frame,and does not show superior seismic performance.However,in the case of medium and large earthquakes,the exceedance probability of the limit state of the RCS frame with asymmetric friction connection is significantly lower than that of the normal nodal frame,which shows excellent seismic performance.