| Stainless steel structure has excellent corrosion resistance and good mechanical properties,it has a wide application prospect in industrial and civil buildings under corrosive environment.However,current researches are focusing on the material and member level,while the stainless steel connections,joints and frames have gained less attention,which hinders the further popularization and application of stainless steel structures,so it is urgent to carry out relevant research.Therefore,this dissertation take the extended endplate joints and welded beamcolumn joints commonly used in the stainless steel frame structures as research objects,and develop the key connection components of the joints.The seismic behavior of the abovementioned joints is studied through experimental study,finite element analysis and theoretical research.The main research work and achievements are as follows:(1)28 smooth round bars and 90 notched round bars of austenitic stainless steel S30408 were tested under the monotonic tensile and ultra-low cycle loads.The monotonic and cyclic constitutive models of austenitic stainless steel S30408 base metal,weld material and heataffected zone material were established by using finite element method.The toughness parameters of the micromechanical models and the material damage degradation parameters under the ultra-low cycle loading were calibrated.The results provided a necessary basis for the fracture performance analysis of subsequent stainless steel beam-cloumn joints.(2)Tests on the physical mechanical properties and torque coefficient of six kinds of stainless steel bolts were carried out and a complete set of technological parameters of stainless steel pre-tension bolts were established.The friction surfaces of 5 stainless steel plates coated with anti-slip paint were tested which made a high slip factor.The test results improved the research and development of the key components of the stainless steel high strength bolt friction type connection.(3)Based on the quasi-static tests of 10 stainless steel and 2 carbon steel high strength bolted extended endplate joints,the failure mode,bearing capacity,ductility,energy dissipation capacity,stiffness degradation,the component of joint rotation,strain distribution and bolt loads were studied.The results show that the stainless steel high strength bolted extended endplate joints had high flexural capacity,energy dissipation capacity and deformation capacity,and good seismic performance.Compared with carbon steel joints,stainless steel joints had obvious stiffness degradation and energy dissipation before yielding,and the nonlinear characteristics were more obvious.(4)Based on the joint test results,the refined finite element model of stainless steel high strength bolted extended endplate joints was developed,and the weld ductile fracture model was introduced,the failure process,moment-rotation relationship,and the time and location of ductile crack initiation of the joints were simulated and verified.Then,and the finite element parametric analysis was carried out on the factors such as endplate thickness and stiffening ribs,column web stiffener,bolt preload,column axial compression ratio and slip factor of the frictional surface to analyze the working mechanism of the joint.Based on the component method,the nonlinear moment-rotation relationship skeleton model in the form of RambergOsgood expression and the linear peak-pointing and nonlinear kinematic hardening hysteretic models were proposed for the joints with different failure modes,all the models were verified to have high accuracy.(5)The refined finite element model of stainless steel welded beam-column joints were developed,and the parameters such as the thickness of the panel zone,the height of the beam section,the thickness of the column flange,the width of the column flange and the axial compression ratio were analyzed to reveal the failure mode and energy dissipation mechanism of the joint.Based on the component method,the nonlinear moment-rotation relationship skeleton model in the form of Ramberg-Osgood expression and the nonlinear kinematic hardening hysteretic models were proposed for the joints.The verification of the finite element results show that the formula have high accuracy.(6)The seismic response analysis model of stainless steel plane frame considering the moment-rotation hysteretic model of the joint were established and the dynamic elastoplastic analysis was carried out,the influence of the joint performance on the overall seismic performance of the frame was revealed,which can provide a certain reference for the design and promotion of stainless steel joints and frames. |
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