Study On Mechanical Properties Of High-strength Steel Nodes After Earthquake

Based on the concept of structural toughness,a wide range of scholars began to pay attention to the post-earthquake damage control and post-earthquake repair performance of structures.The industrialization of modern buildings has put forward new requirements for green prefabricated structures,so as to enhance the ability of rapid recovery of buildings after the earthquake.This paper presents a controllable and fast repair under seismic action.The structural design,theoretical calculation and ABAQUS finite element analysis are conducted to discuss the influence of each parameter on the mechanical properties of nodes.Then the new node is assembled in a three-layer steel frame structure to test the fuse function of the T-type connector.Through the static and dynamic analysis,the stiffness of the flange of the T-type connection is calculated under the influence of the bolt pre-tightening force and bending stiffness.The main research work and the conclusions are summarized as follows:(1)The preliminary theoretical design and calculation of the connection form and construction of the nodes are made.Nodes by the upper and lower two T type connection and the central pin shaft connecting beam and column,earthquake,make the T type connector fully energy consumption and take the lead into the plastic state,pin shaft provides certain vertical support for beam,ensure the beam,column main structure in the elastic stage not damage,after the earthquake replacement up and down T type connection can make structure function quickly recovery,effectively avoid the economic loss of the main structure,improve its whole life cycle.(2)Four influence parameters(energy consumption section length,thickness,steel strength and connection form)are selected for parametric analysis of each series of nodes.The analysis results show that the stiffness of the node is large when the length of the energy consumption segment is too short,and the bearing capacity of the node exceeds 1.4b_f(b_fis the beam width).The length of the energy consumption section should be taken(1.2～1.4)b_f.The thick web is not conducive to its plastic deformation and affects the ductility of the node.Therefore,according to the analysis results,it is suggested that the thickness of the energy-consuming section should be taken(1.0～1.17)t_w(t_wis the thickness of the beam flange).The new node using Q460 high strength steel showed good seismic performance,and the ductility coefficient reached more than 3.0.The damage patterns of different nodes under different connection and weakening forms are similar,and the damage distribution is mainly distributed in the abdomen,and the bearing capacity and initial stiffness of each node are less than 4%.(3)The BASE specimen is assembled in a three-layer steel frame structure,and the static thrust analysis and dynamic time course analysis are analyzed with the traditional welding node and plate reinforced flange transition joint.The results show that the T-type connecting steel frame conforms to the design expectation of damage control,and the bearing capacity only drops by 2.92%at the Angle is 0.05 rad,and the T-type connector as the structural fuse node has good damage control ability and rapid recovery in the steel frame,and the maximum displacement angle in the rare earthquake.(4)The initial stiffness of T-type connection under the influence of bolt pretension and bending stiffness is calculated and compared with the simulated value.The results show that the existing theory of T-type connection stiffness overestimate the rotational stiffness of nodes and its accuracy needs to be improved.The initial stiffness of the T-type connection considering the bolt bending stiffness is 1.2 times higher when not considered.Therefore,in the bolt connection with pretightening force,the bending stiffness of the bolt cannot be ignored when calculating the initial stiffness of the T-type connection.