Study On Mechanical Behavior Of Stud Shear Connectors Of Double Steel Plates And Concrete Composite Shear Wall At Ambient Temperature And After Fire

The double steel plate concrete composite shear walls is mainly composed of steel plates,concrete and shear connectors.Studs,as the most commonly used shear connectors to ensure the interaction of steel plates and concrete,have achieved a lot of results in bearing capacity based on composite beams and slabs at ambient temperature.At the same time,the studs design of the double steel plate concrete were base on the research results of the composite beams and slabs.However,the boundary conditions and stress modes of the studs in the composite shear wall are very different from the studs in the composite beams and slabs,and there the researches on the residual performance after fire are rare.In this thesis,the push-out test of stud connection of double steel plate concrete composite shear wall at ambient temperature and after fire are carried out,and completed the corresponding numerical simulation and parameter analysis,the main research work is as follows:(1)Three push-out tests of stud connectors of double steel plate concrete composite shear wall are carried out to study the influence of stud length and stud arrangement on its performance.The test results show that the failure modes of specimens with different parameters are the same: all the studs are sheared,and the concrete is partially crushed,The steel plate-concrete load-slip curve of the specimen can be divided into four stages: linear elasticity rising stage,curve rising to ultimate bearing capacity stage,horizontal and curve falling stage,and bearing capacity remaining stage.Compared with the 3×3 arrangement and the stud length L=55mm,the bearing capacity of the same arrangement and the stud length L=70mm increased by 4.7%,and the ultimate slip increased by 5.2%,while the 3232 plum blossom arrangement and the stud length L=55mm,The bearing capacity increased by 8.8%,and the corresponding ultimate slip increased by 12.5%.(2)Completed two sets of three pairs of steel plate-concrete composite shear wall stud connectors that were heated to ISO-834 standard for 60 minutes and 90 minutes respectively after being fired.And study the stud length,stud arrangement and fire time on stud performance.The test results show that the damage form of the specimen after fire is the same as that at ambient temperature,all the studs are sheared,and the concrete is partially crushed.The loadslip curve of the specimen after fire is similar to the specimen at normal temperature,and can also be divided into four stages.Compared with specimen at ambient,the bearing capacity of the specimen decreases after fire,the stiffness of the rising section of the load-slip curve decreases significantly,and the ultimate slip increases.The bearing capacity of specimens exposed to fire for 60 minutes decreased by a small amount(maximum of 4%),and the bearing capacity of specimens exposed to fire for 90 minutes decreased by approximately 25%;When the fire time is the same,the load capacity of the 3×3 arrangement and stud length L=70mm specimens is increased by 5%(60min fire)and 4%(90min fire)compared with the 3×3 arrangement and the stud length L=55mm.The bearing capacity of the plum blossom arrangement specimens is increased by 8%(60min on fire)and 9%(90min on fire).The influence of stud length and arrangement on the bearing capacity of the specimen after fire is basically the same as that of the specimen at ambient temperature.(3)The finite element software ABAQUS was used to simulate the push-out test,fire test process and temperature field of the double steel plate concrete composite shear wall stud connector at ambient temperature and high temperature.The simulation analysis results are in good agreement with the test results,indicating that the selected modeling method,material thermal parameters,material constitutive and contact simulation are more reasonable and reliable.Using proven finite element modeling methods,expanding the parameters of stud diameter,length,spacing,arrangement,etc,completed the finite element parametric analysis of 28 sets of stud connectors at ambient temperature,and using the maximum temperature experienced by the stud root and different stud diameters as parameters,18 groups of parametric analysis of the mechanical properties of stud connectors after fire were conducted.According to the results of the parameterized analysis,the calculation formula of the bearing capacity of the stud connector of the double-steel concrete composite shear wall considering the stud diameter,stud length,stud spacing and the maximum temperature experienced by the stud root fitted.