Experimental Research On Fire Resistance Of Axial Compression H-section Stainless Steel Columns With Restraint

Now,pre-fabricated buildings in China is being vigorously promoted,thereby reducing environmental pollution and improving the level of productivity.The advantage inherent assembly characteristics of steel structure will further promote the development of steel structure.As a member of the steel family,the stainless steel has been gradually applied to the building structure because of its superior corrosion resistance.The publishing of "Technical specification for stainless steel structures"(CECS410-2015)will speed up the application of stainless steel in building structure.However,in recent years,the construction fire has occurred frequently,which has brought serious damage to the safety of the building structure.The test research and theoretical research of fire resistance for ordinary steel structures have become the main direction of building fire resistance research,while there are few studies on the fire resistance of stainless steel structures or components.The research on the fire resistance of stainless steel columns at home and abroad is focused on the study of rectangular(square)closure columns,while the beam and column nodes of the actual frame are generally rigid or semi-rigid nodes and the columns will be affected by the axial restraint and rotation restraint of the connected members by thermal expansion in fire.Therefore,it is necessary to consider the effect of restraint on the fire resistance of stainless steel columns.Based on the background above,an experimental study and numerical simulation of stainless steel columns with axial restraint and under rotation restraint compression loads in fire were conducted,which indicated the behavior response and failure mechanism of each specimen.Furthermore,the relevant fire resistance design recommendations are given in the paper.Based on the domestic S30408 austenitic stainless steel material,the material mechanical property tests under both room and elevated temperatures were carried out,and the steady tests at elevated temperature are conducted to investigate material mechanical properties of stainless steel.The test results show that,at room temperature,the latest strain-strain curve calculated by the strain hardening index correction formula proposed by Arrayago et al.is in good agreement with the overall test data curve;at high temperature,the stress-strain curve calculated by strain hardening index correction formula proposed by Ju Chen and Xia Xinfeng are both in good agreement with the experimental data curve.In order to investigate the influence of axial restraint and rotational restraint on the fire resistance of stainless steel columns based on mechanical properties of materials under high temperature,fire test study of five H-section stainless steel columns with axial restraint and two H stainless steel columns with axial restraint and rotation restraint were conducted,which indicated the behavior response and failure mechanism of each specimen.Through the fire test,the furnace temperature-time curve,the surface temperature-time curve of the specimen,axial displacement-time(temperature)curve,the lateral deformation-time(temperature)curve,and specimens' failure morphology are caught from each test specimen.At last,the test results were analyzed to determine the flexural temperature and critical temperature of the tested stainless steel columns.Nonlinear analysis software ABAQUS was used to establish the finite element analysis model of each test specimen in the fire test,which was carried out numerical simulation analysis on the behavior of each test specimen to verify the accuracy and feasibility of the finite element model.Based on the finite element model above,parametric analysis is carried out on the H-section stainless steel columns with restraint under axial compression,which mainly includes single parameter analysis and parametric coupling analysis.The results showed that the fire resistance of stainless steel columns in different cross section are slightly different under the same conditions;The ratio of load ratio n,slenderness ratio ?,axial restraint stiffness ratio ?1 and rotational restraint stiffness ratio ?r are the key factors influencing the fire resistance of H-section stainless steel column with restraint axial compression;The increase of Load ratio n,slenderness ratio ? and axial restraint stiffness ratio?1 all reduce the fire resistance of stainless steel column.Load ratio n and axial restraint stiffness ratio ?1,slenderness ratio ? and axial restraint stiffness ratio ?1,slenderness ratio ? and rotation restraint stiffness ratio ?r are coupling between the two parameters.Therefore,the interaction between the above parameters should be taken into account in the analysis of the fire resistance of the H-section stainless steel columns with restraint under axial compression.According to the experimental data and numerical simulation results,the determination of critical temperature for H-section stainless steel column with the rotation of the end is equivalent to the axially restraint H-section stainless steel column with the two ends hinged,and the corresponding calculation table is given.Based on the coupling of the axial stiffness ratio ?1 with the ratio of slenderness ? and Load ratio n,an explicit simplified formula for the critical temperature of axially restrained H-section stainless steel columns under fire is proposed.The results of the simplified formula are compared with the finite element results and the experimental results respectively,which verify the accuracy of the simplified formula.