Experiment And Numerical Simulation On Fire Performance Of Concrete Filled Stainless Steel Tubular Columns

As stainless steel is being widely used in engineering structures in recent years,concrete filled stainless steel tubular (CFSST) columns, which have favorablemechanical and economical properties, have become more and more attractive amongresearchers. It is very important to investigate the performance of CFSST columns.This paper thus evaluated the fire performance of CFSST columns through bothexperimental and numerical methods. The main research work and achievements aresummarized as follows:(1) Fire experiments were carried out on full scale circular and square CFSSTcolumns with constant axial load on both ends. All sides of the columns were exposedto fire according to ISO834standard curve. The parameters include: the axial loadlevel, sectional dimension of CFSST columns. Axial displacement-time curves,sectional temperature-time curves, failure modes and fire resistances of the testedcolumns were recorded during the experiments. The influences of the parametersconsidered on the failure modes and fire resistance of the columns were investigated.The results showed that CFSST column shows good performance under fire and itsfire resistance is dramatically affected by the load level and cross-sectionaldimension.(2) A finite element analysis (FEA) model to simulate the behaviour of CFSSTcolumns under both axial load and high temperatures was introduced in whichsequentially-coupled thermal-mechanical analysis method was adopted. The FEAmodel considered both geometrical and material nonlinearity, thermal properties ofconcrete and stainless steel, heat resistance and interaction between the interfaces ofconcrete and stainless steel, initial imperfection and actual end conditions, etc. TheFEA model contains temperature analysis module and thermal-mechnical analysismodule, and both were verified by extensive experimental results, including results offire tests from other researchers and from the author.(3) The failure modes, deformation development, internal force transfer mechanism, stress versus time relations, strain versus time relations and contact stress versus timerelations of CFSST columns during the whole process of heating according to ISO834standard curve were understood by means of the FEA model. Furthermore, thefailure mechanism of the CFSST columns under fire was analyzed.(4) A comprehensive parametric study was conducted. Influence of the parameters onthe fire resistance of CFSST column was analyzed. The parameters include: the loadlevel, the slenderness of the column, sectional dimension, material properties ofconcrete and stainless steel, etc. It showed that the fire resistance of CFSST column issignificantly influenced by the load level, the slenderness and cross-sectionaldimension of the column. Other parameters, such as the steel ratio, strength ofconcrete and stainless steel, have moderate affects on the fire resistance of CFSSTcolumn.