Study On Effect Of Fire Combustion Patterns On Mechanical Behavior Of Concrete Filled Steel Tubular Short Column After Exposure To Fire

In recent years,the frequent occurrence of fire accidents in the construction structure has attracted the attention of the society.Research on fire and post-fire behaviours of square CFST columns is deepened.Modern buildings are developing towards diversification and specialization with the different shapes of architectural interior features,which results in different fire characteristic s of different buildings.The single curve is usually adopted when domestic and foreign scholars conduct fire-resisting research,however,there is less research on different characteristics of fire.In order to study the effect of different fire burning p atterns on the mechanical properties of square CFST columns,the following work is carried out in this paper :(1)A mathematical model of building fire was built based on the architectural space characteristics and the properties of combustible materials in the buildings,and the actual fire rising and cooling curves of different building Spaces are obtained;The concept of equivalent exposure time was introduced.And this paper uses two methods to make the actual fire rising and cooling curve equivalent to the ISO 834 standard curve formulated by the international standard organization;The temperature field curves of different positions in the middle section of the square CFST columns are analyzed after high temperature test of different fire burning patterns.(2)A total of sixteen square CFST columns were tested under the whole fire process and twelve of them were tested for axial stress.The influence of axial compression ratio and fire burning patterns on the mechanical properties of the square CFST column is investigated in the case of fire protecti on layer.The influence of the above parameters on the mechanical properties of the square CFST column is explained in terms of mechanical property and damage mechanism of the material.This paper also discussed the influence of two parameters on the failure mode,the axial compression stiffness reduction and the residual capacity coefficient.(3)The temperature field analysis model of square CFST columns is established by using the ABAQUS finite element analysis software and the results are compared with the experimental results.The axial compression test results are compared with previous studies and the influence of each parameter on the post-fire behaviours of square CFST columns is described.