Fire Resistance Of Cold-formed Light Gauge Steel Frame Floor Systems In Standard Fire

Cold-formed light gauge steel framing(LSF)structure is a type of fabricated steel structure.It is composed of steel stud or joist and steel track,and two sides of LSF through self-tapping screws connected to cover structural panels and fireproof panels,which are made of building panels with fireproof,sound insulation properties,and fire resistance of LSF is the main problem that needs to be solved urgently.At present,the number of fire tests for LSF floor systems is limited,and most numerical simulations only carry out two dimensional heat transfer analysis for the middle section of the structural system,or conduct thermal-mechanical coupling analysis of specimens based on the test temperature.This is still significantly different from the real three-dimensional heat transfer situation,and the results of two-dimensional analysis can not effectively show the temperature distribution of the structure under three-dimensional heat transfer conditions.In order to more accurately study the fire resistance of LSF floor systems,this paper used ABAQUS finite element software to establish three-dimensional heat transfer models and three dimensional thermal-mechanical coupling models of two LSF floor systems,and studied the nonlinear heat transfer process and the structure characteristic of thermal-mechanical coupling behavior under ISO-834 standard fire condition.Secondly,a numerical simulation modeling method that could better reflect the contact force relationship and connection mode between the fireproof panel and LSF was proposed.Compared with the fire test results showed that the proposed three dimensional heat transfer model and the three dimensional thermal-mechanical coupling model can fully describe the temperature distribution and structural deformation of LSF floor systems in fire.The calculated temperature rise of the structural system,the deflection deformation trend of specimens and the final failure mode were in good agreement with the test results,which verified the validity of the numerical model.Finally,by changing the types of fireproof panels,thickness of fireproof panels,joist section height and joist spacing of LSF floor system,the influence of different structural parameters on the fire resistance of the floor system was simulated and analyzed.The simulation results show that:(1)In the case of the same thickness,the fire resistance of LSF floor system using magnesium oxide board is significantly better than that of calcium silicate board and gypsum board,and the fire resistance of LSF floor system using calcium silicate board is the worst;(2)Increasing the thickness of the fireproof board can obviously increase the fire resistance time of LSF floor systems,and the time can be extended by more than 25%for each increase of 8mm plate thickness;(3)When the height of the joist section increases from 100mm to 260mm,the fire resistance time of LSF floor system is increased by 3.5%;(4)When the distance between the joists increases from 300mm to 900mm,the fire resistance time of LSF floor system is reduced by 6.5%,which has little effect.