| At present,CFST columns and steel-bars truss deck are more and more used in various type of building load-bearing components.When a fire occurs,their fire resistance are related to the overall safety of the building.In the structural design,fire resistance is a difficult point that must be considered.However,at present,fire resistance design is still in the development stage,and the relevant specifications and researches at home and abroad are not comprehensive.Therefore,it is of great theoretical and practical significance to intensive study the fire resistance of CFST columns and steel-bars truss deck.In this paper,based on the design parameters of practical engineering components,the thermal and mechanical properties of materials were determined based on the domestic and foreign codes and the research of scholars.ABAQUS finite element analysis software was used to establish the calculation model of CFST column and steel-bars truss deck,and the correctness of the model was verified by comparing with the calculation formula of material mechanics.Under the standard temperature rise curve,the temperature field of CFST column and steel-bars truss deck was calculated respectively,and the component temperature field was determined.By calculating the fire resistance of CFST columns under different axial load ratios for 3hours under axial compression,and fitting the scatter diagram of axial load ratio-axial displacement,the maximum axial load ratio bearing limit of CFST columns under axial compression is 0.41.By calculating the fire resistance of CFST columns under different axial load ratios and fitting the scatter diagram of axial load ratio-fire resistance,the curve and calculation formula of axial load ratio and fire resistance of CFST columns under axial compression were established.A method to judge the fire resistance performance and fire resistance limit of CFST columns by axial load ratio under fire was proposed.By calculating the horizontal displacement and axial displacement of CFST columns under the combined action of compression,bending and shear,the variation trend of horizontal displacement and axial displacement with shear and bending moment and the influence of shear and bending moment on the fire resistance of columns were analyzed,the fitting curve of shear load ratio-horizontal displacement was given.By comparing with the fire resistance of the column under axial pressure,the applicability of the method for determining the fire resistance and fire resistance limit of columns under complex axial loading was verified.By calculating the fire resistance performance of steel-bars truss deck with different span,different cover thickness and with or without steel truss,the variation trend of vertical displacement in the middle of span with different parameters was analyzed,and the influence of different parameters on the fire resistance performance of steel-bars truss deck was determined,which provided suggestions and reference for the determination of plate parameters in practical engineering.For the fire resistance calculation of CFST column and steel-bars truss deck,this paper has the following innovations:(1)Combined with scholars’ research on the fire resistance of CFST columns under compression-bending and shear-compression,this paper established the calculation model of fire resistance of CFST columns under compression,bending and shear,and analyzed the influence of shear and bending moment on the fire resistance of columns.(2)In this paper,the variation of fire resistance and fire resistance limit of CFST columns with load ratio was revealed.A method to judge the fire resistance performance and fire resistance limit of CFST columns under axial compression and combined action of compression,bending and shear was proposed.(3)For the lack of relevant research results of steel-bars truss deck under fire,this paper made a preliminary study on the parameters affecting the fire resistance performance of steel-bars truss deck,analyzed the influence of different parameters on the fire resistance performance of steel-bars truss deck,and provided a reference for the further research of steel-bars truss deck.The research results of this paper can provide basic data support and reference for fire resistance analysis of CFST columns and steel-bars truss deck. |
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