Study On Fracture Performance Of Weld Of Cover-plate Reinforce Connection In Steel Frame

The innovative steel structure beam-column connection which relocate the plastic hinge is put forward by experts and scholars,who aim to make further study about steel structure connection after the American Northridge earthquake and Japanese Kobe earthquake,and become a hot topic among the steel structure research.By moving the plastic hinge far away from the beam-column interface,cover-plate reinforced connection,which is welded a cover-plate at the beam-end,achieves the purpose of protecting the welds of connection and improving the mechanical behavior during the earthquake and becomes a beam-to-column connection which is recommended by FEMA-350.However,the existing research of cover-plate reinforced connection is concentrated on the mechanics part,and the research of the fracture performance of the connection is deficient.Therefore,a large amount of experimental investigations and numerical analysis are carried out in this paper to study the fracture behavior of the cover-plate reinforced connection,especially the fracture behavior of welds in the reinforced area.The main research works and achievements covered in this dissertation are as follows:(1)In this paper,three sets of 12 local weld region specimens(CP-1、CP-2、CP-3)originating from the welding zone of the bottom beam flange of cover-plate reinforced connection were tested under monotonic loading.Among them,CP-1、CP-2 were in same intensity and different thickness.CP-2 、 CP-3 were in same thickness and different intensity.The test was divided into two stages.In the first stage,taking no initial damage specimen(CP1A1,CP1A2,CP1A3)as the study objects,studied the effect of loading rate on the fracture properties of connection welds.In the second stage taking specimens with initial damage(CP1DT1、CP1DT2、CP1DT3、CP2X、CP2DT3、CP2DG、CP2JT、CP2JG、CP3X)as research objects,analyzed the effects of defect parameters,strengthening plate thickness and material strength on the fracture properties of connection welds.(2)The numerical finite-element model of local weld region was established bythe ANSYS software to further study the influence of the thickness of the strengthened plate,the material strength and the strength matching between reinforcement plate and beam-column on the fracture properties of connection welds,at the same time the computer simulation result was compared with the experiment results.(3)By means of indirect coupling method and birth-death element of ANSYS software,this paper simulated welding process of local weld region to get the dynamic temperature field and residual stress field and analyzed designed research paths of the time history of temperature and the distribution of residual stress.The monotonic tensile simulation is carried out on the basis of residual stress analysis,and the influence of residual stress at different positions on the fracture properties of connection welds is analyzed.