Fire Performance Tests And Numerical Simulation Of Air-supported Membrane Structures

The air-supported membrane structure is a new type of structure with coated fabric membrane as the main material,which is filled with sufficient air in a closed large space and relies on the internal and external pressure difference to replace the supporting components such as beams,columns and frames.It is widely used in sports venues,exhibition centers,transportation hubs,industrial storages and other major projects.The research on fire performance of air-supported membrane structures has been not available,which brings difficulties to the design and examine.At the same time,the fire resistance classification of buildings is determined by the combustion performance and fire resistance limit of the components in the existing building fire protection specifications.The air-supported membrane structure is holistic,and the high temperature performance of the membrane material and its connection material is different from that of the conventional building materials.Therefore,the evaluation criteria of the existing specifications cannot be used for air-supported membrane structures.Therefore,this paper takes the air-supported membrane structure as the research object to carry out a series of fire tests,and proposes a numerical simulation method for air-supported membrane structures’ fire based on the test results,the main research contents of the paper include:(1)Experimental study on mechanical properties of membrane materials at high temperatureThe high temperature tensile test,high temperature stress relaxation test and tensile test after high temperature exposure were carried out on PVC membrane materials.The high temperature tensile properties of membrane materials were obtained,and the attenuation law of initial stress at high temperature was studied.Based on the tensile test after high temperature exposure,the changes in mechanical properties of materials after the fire were discussed.(2)Experimental study on mechanical properties of lap welded seams at high temperatureThe tensile properties of lap welded seams,single-side coating lap welded seams and double-side coating lap welded seams at high temperature were obtained by experiments.It was found that the three kinds of lap welded seams almost lost the load-bearing capacity at 120°C,and the high-temperature performance of single-side lap welded seams was better.(3)Fire test of the full-scale air-supported membrane structureThe first fire damage test of the new type of full-scale air-supported membrane structure was carried out,and the fire test scheme suitable for the air-supported membrane structure was designed.The UAV radar ranging technology was used to obtain the deformation of the air-supported membrane structure in the fire test.The test found that the failure of the air-supported membrane structure first occurred at the lap welded seam,which was characterized by large deformation and an obvious increase in internal pressure compared with the traditional steel structure fire.This test provides a unique basis for the verification of subsequent numerical simulation methods.(4)Fire internal pressure simulation of air-supported membrane structuresThe internal pressure simulation of air-supported membrane structures needs to consider the leakage area,air intake volume and ambient temperature.Based on the simulation results of internal pressure under fireless conditions,the prediction formula of leakage area in closed space was proposed.A fire internal pressure simulation method of air-supported membrane structures was proposed,which considered gas leakage and frequency regulation of air intake volume.Based on the above methods,the influence of fire location,fire power and fire growth rate on internal pressure was studied.It is found that the fire location has no effect on internal pressure,and the peak internal pressure is higher as the fire source power and fire source growth rate increase.(5)Study on fire temperature of air-supported membrane structuresBased on the combustion test and the corresponding numerical simulation of the membrane and the lap welded seam,the simulation method and pyrolysis parameters of the membrane and the lap welded seam were determined.The internal pressure time history,air temperature curve and damage location obtained based on FDS were in good agreement with the fire test.Through the temperature simulation of airsupported membrane structures’ fire with different fire power and different fire location,it is found that air-supported membrane structures’ fire has typical ’thermalpressure’ coupling effect,and the roof temperature is ’non-uniform time-varying’.However,the roof damage time of the simulation method is later than that of the fire test,indicating that the simulation method considering material pyrolysis is unsafe for the fire damage research of air-supported membrane structures.(6)Thermo-mechanical coupling study of air-supported membrane structuresBased on the created interface program of ABAQUS,the non-uniform timevarying temperature of membrane surface and the internal pressure were introduced.Based on the elastic modulus of the membrane material and the lap welded seam at high temperature and the Hashin failure criterion,the ‘thermo-mechanical’ coupling analysis method suitable for the fire damage of air-supported membrane structures was proposed.The simulation results are in good agreement with the fire test.The fire damage of air-supported membrane structures should be simulated based on the‘thermo-mechanical’ coupling analysis,and the fire damage of air-supported membrane structures can be attributed to the coupling effect of high temperature and high pressure of the fire.The high temperature degrades the tensile properties of the membrane and the lap welded seam,and high pressure brings higher loads,resulting in the lap welded seam being pulled off first.