Research On Fire Resistance Performance Of Double Skin Composite Wall With Steel Truss

With economic development in China,the number of high-rise and super-high-rise buildings is increasing rapidly.The composite wall structure has attracted much attention due to high capacity,good ductility and great stiffness and the structural form is constantly innovative.Double skin composite wall with steel truss is a new type of composite wall.The double skin plates are connected by steel trusses,thus forming several vertically connected cavities and concrete is filled between the steel faceplates during the construction stage.Double skin composite wall has a bright prospect in high-rise buildings.However,high-rise building fires have occurred frequently which cause serious harm to the safety of structure in recent years.Therefore,it is particularly urgent to study the fire resistance of the structure.This paper carried out experimental research and numerical simulation on the fire resistance of double skin composite wall with steel truss and revealed the temperature rising behavior and mechanical properties under fire.Finally,this paper put forward the corresponding fire resistance design methods.The main contents are as follow:The one-side fire tests of six double skin composite walls with steel truss were carried out following ISO-834 standard heating process.The effects of the spacing of steel truss,the thickness of steel faceplate,axial compression ratio and the thickness of fireproof coating on the fire resistance of double skin composite walls with steel truss were investigated.The behavior response of double skin composite walls with steel truss under fire was revealed.Through fire tests,the temperature-time curve,the axial and lateral displacement-time curve,the deformation features and the fire resistance limit of each specimen were obtained.Fire test results showed that:(1)Four specimens without fire protection reached the fire resistance limit due to the failure of thermal insulation;Two specimens with fire protection had a fire resistance limit of more than 180 minutes;(2)The thickness of fireproof coating has a significant effect on the fire resistance limit of specimens while the influence of axial compression ratio,the thickness of steel faceplate and the spacing of steel truss is limited.The finite element software ANSYS was used to establish accurate finite element models of double skin composite walls with steel truss.Through the method of thermal-mechanical coupling analysis,the fire resistance performance of the specimens was numerically simulated.The analysis models include temperature field and fire resistance limit of the specimens.The numerical results were compared with the experimental results to verify the accuracy of the finite element model.The parametric analysis was carried out by the verified finite element models to analyze the influencing factors(the fire protection thickness,axial compression ratio,wall thickness,the height-width ratio,the height-thickness ratio,the spacing of steel truss,the thickness of steel faceplate,steel strength and concrete strength)on the fire resistance performance of double skin composite walls with steel truss under one-side and double-side fire conditions.The results showed that:(1)The wall thickness and fire protection thickness are the main factors that affect the fire resistance limit of double skin composite walls with steel truss under one-side fire condition;(2)The height-thickness ratio,wall thickness,axial compression ratio and fire protection thickness are the main factors that affect the fire resistance limit of double skin composite walls with steel truss under double-side fire condition.Based on the results of parametric analysis,the simplified formulas for calculating the fire resistance limit and the fire protection thickness of double skin composite walls with steel truss were deduced which were found to be in good agreement with experimental and numerical results.The simplified formulas are simple and convenient which can be referenced in engineering practice.On this basis,suggestions for fire protection design of double skin composite walls with steel truss were given.