Study On Seismic Performance Of Buckling-restrained Braced Semi-rigid Steel Frame

Semi-rigid jointed steel frame is a kind of steel frame with bolted connection,with good ductility but insufficient lateral stiffness resistance,therefore,it is necessary to increase the support members to improve the lateral stiffness resistance of the structure.As a kind of displacement type dampers,the buckling restrained brace(BRB)has gained extensive utilization for reinforcing both new and existing buildings domestically and internationally because of its advantages of improving lateral stiffness and energy consumption stability,etc.BRB combined with semi-rigid steel frame to form BRB semi-rigid steel frame can have the advantages of good ductility,high stiffness and energy consumption stability at the same time.However,the nodal plates of BRB are directly welded to the beams and columns,and it forms a rigid constraint in the nodal region,which limits the semi-rigid nodal deformation of the frame and leads to the ineffective performance.Therefore,this paper adopts the way that the nodal plate of BRB is only connected to the frame column to realize the combination of BRB and semi-rigid steel frame and make full use of their respective strengths.This article validates the reasonableness and dependability of the adopted connection method through theoretical analysis,test and finite element analysis go a step further,and investigates the seismic performance of the BRB semi-rigid steel frame based on this connection method.Here are the primary research topics:(1)The seismic performance of BRB semi-rigidly connected steel frames is investigated through 4 tests by first determining the nodal plate and column connection method through theoretical analysis.The test results show that the combination of BRB and semi-rigid frame can be achieved by connecting the nodal plate to the column and giving full play to the respective advantage of both.Meanwhile,the incorporation of BRB can significantly enhance the seismic performance metrics,including stiffness,bearing capacity,and energy dissipation capacity of semi-rigid steel frames.The integration of BRB with semi-rigid steel frames produces a structural system that exhibits excellent seismic performance.(2)To confirm the validity and dependability of the model,a finite model of BRB semi-rigid steel frame is constructed using ABAQUS software.Based on the finite element standard model,further analysis of the influencing parameters of the structure was carried out.During the investigation,it was discovered that the stiffness and load capacity of the structure were minimally affected by the beam-column steel yield strength and bolt preload at semi-rigid nodes.However,enhancing the yield strength of the angle steel,increasing the thickness of the angle,and augmenting the yield load capacity of the BRB were found to be effective measures for improving the structure’s stiffness and load capacity.Furthermore,increasing the yield strength of the angle steel and angle thickness resulted in delaying the angle’s entry into the yield state.(3)The design method that the nodal plate is connected to the frame column by bolts or welding is proposed;the conditions of BRB as the first line of defense in semi-rigid steel frame are summarized by deriving the yielding displacement of flexural restrained bracing and the yielding displacement of semi-rigid steel frame,and the numerical simulation analysis is carried out to verify them,which provides reference for the application of this structural system in practical engineering.