Seismic Performance And Design Method Of Sliding Gusset Connections In Buckling-restrained Braced RC Frame

The buckling-restrained brace(BRB)is an efficient energy-dissipating damper that yields in both tension and compression to dissipate seismic energy.And the BRBs have been widely adopted to the seismic design of new structures and existing structures around the world.It is common to connect the BRBs with the frame by welded joints.However,recent studies have revealed that the BRB-frame joints or substructure of brace span fail under large deformations,due to the strong tangential constraints caused by the welded joints on the opening and closing deformations of beam-column joints.Then,the BRB will fail in the extreme earthquake events and cannot prevent the structures from collapsing.The solution to this problem is not only significant for BRB to fully dissipate seismic energy,but also improve the resistance to collapse of BRB-frame structure.Therefore,this paper proposed two novel types of BRB-RCF sliding joints,i.e.sliding anchor plate(SA)and sliding gusset plate(SG).In the former,the sliding surface is set between the anchor plate and concrete.As for the latter,the gusset plates are connected with the associated RC beams and columns by post-tensioning high-strength studs,where the sliding surface is set between gusset plates and concrete.In this paper,the construction plan,seismic performance,force transmission mechanism and design method of the above two types of joints were systematically studied through experimental tests,numerical simulations and theoretical derivation.The main content and the corresponding conclusions are as follows.(1)First of all,Chapter 2 proposes two types of joints,SA and SG,that use slip deformation to release the tangential constraint between the joint plate and the beam and column.The second chapter described the specific structure,working principle and construction process of SA and SG as well as investigated the feasibility of the BRB-RCF sliding joints.Compare the difference between the welding joints and the sliding joints from the aspect of the force form.Then,the design method of BRB-RCF sliding joints was detailed proposed from a series of aspects,such as the design of anchor plate,embedded parts and the transmission of plastic hinges,which formed the basis for the design of the test models in the following chapters.(2)In the third chapter,five test models for sliding joints were designed according to the methods in the second chapter: one for the traditional joints as the control group,two for sliding anchor plates,and two for sliding gusset plates.And the two models in each experimental group are used tested for the reinforcement scheme with or without transferred plastic hinge respectively.The overall performance,BRB mechanical performance,beam-column mechanical performance and the mechanical behaviors of joints of the tested substructures are obtained through the pseudo-static cyclic loading of the five test substructures.By comparing the above test results,we initially verified the seismic performance of the SA and SG joints as well as found that both can effectively weaken the opening and closing deformations of traditional brace.(3)According to the test models in the third chapter,the fourth chapter firstly developed the finite element models(FEMs)by ABAQUS.The simulation models are verified through the comparison of the results of simulation models and test models.Next,the parameter analysis of FEMs were conducted on the five models with different angles of brace,in order to further clarify the mechanical performance of the SA joints.Then we analyzed the bearing performance of SA joints under the action of a single brace force and proposed a prediction formula for the action position of the equivalent tension point on the connecting edge of the joint plate.Finally,we investigated the combined effect of the brace force and the opening and closing deformation on the five FEMs.The results of FEM analysis show that the joints can still achieve the design goal of basically maintaining elasticity under the combined action,even though only the brace force is considered in the design method.