| The seismic damage research of Kobe earthquake in Japan and Northridge earthquake in America at the end of last century shows that the traditional common rigid beam-column node connection welds are easy to cause brittle fracture during strong earthquake,which caused a large decline in the overall structure's bearing capacity and ductility performance.In order to solve the problem,many experts and scholars proposed the new types of ductility nodes.Haunch reinforced node is one type,it can improve nodes' mechanical performance such as the stiffness,bearing capacity and limit the displacement,the mechanical properties in the plastic period.Researches at home and abroad are mainly focus on seismic performance research of the steel frame ductility node energy consumption under low cycle load,but the nonlinear dynamic time history analysis of steel frame structure research is less.Research on dynamic elastic-plastic characteristics of enhanced nodes energy consumption space steel frame was conducted on this paper.The domestic and foreign relevant norms were chosen as reference,three single span two truss four-story space steel frame models including symmetrical haunch-reinforced node frame on the top and bottom of beam flange(SHF),beam bottom flange asymmetric haunch-reinforced node frame only on the bottom of beam flange(AHF)and reduced beam flange frame(RBF),and as a comparison a common ordinary node space steel frame(NSF)was designed.Using ANSYS finite element software,input three 8 degrees seismic waves and analyzed seismic performance of the four frames mentioned above,including the displacement,column bottom shear force and response acceleration,and stress distribution of beam-column node area,plastic hinge formation and out-shifted mechanism.Using SAP2000 to check some part of the ANSYS simulation results,at the same time analyzed the floor,stiffener and weld factors effect on the performance of the node,research conclusions are as follows:1 ? The modal analysis shows that: the change of node form will not change structure modal shapes,the frequency and cycle of the structure affected slightly by node form changes,haunch reinforced nodes will make the structure increasefrequencies and decreases cycle.2?The time history analysis shows that: the rules of haunch reinforced nodes' displacement curve,bottom of the column shear force curves,response acceleration amplify coefficient curves are same with other two nodes;It will reduce the capital displacement,increase slightly the column bottom shear force,amplify coefficient are almost the same;The stress level of four frames is close during elastic stage,the stress concentration phenomenon is not obvious,during elastic-plastic stage SHF?RBF?NSF respectively have large plastic zone area and concentrating stress at the haunch end ? weakening area and beam end.Like reduced beam nodes,haunch reinforced nodes can let plastic hinge away from beam end,protect weld at beam column node area,but its location and mechanism are different.3?The time history simulation results of SAP2000,the elastic stage is basically same with the ANSYS results,displacement and shear force result is larger during elastic-plastic stage and structural plastic hinge mechanism is beam hinge mechanism,using SAP2000 to do nonlinear analysis on steel frame is feasible and the result is relatively accurate.4?The floor slab and steel beam form composite beams,and improve the structure stiffness and bearing capacity,reduce the level of stress on flange of the beam end,but it also partly reduce the energy dissipation capacity of structures.The right setting of stiffener ensures local stability of beam components and concentrated force is passed on,which can effectively reduce the stress of the node area.Weld and its through hole should be designed based on the specification,because it decides impact of haunch reinforced nodes can work or not. |
PDF Full Text Request