REVIEW OF MATERIAL PROPERTIES FOR PREDICTING THE FIRE RESISTANCE OF CONCRETE-FILLED STEEL SQUARE TUBE COLUMN USING THE NUMERICAL METHOD

摘要

The authors have examined the experimental results on the fire resistance of concrete-filled steel square tube (CFT) columns without fire protection. Twenty CFT column specimens, with 300-400-mm square or circular sections, were heated for 2 hours in accordance with KSF 2257 (equivalent to ASTM El19 and JIS A 1304). To evaluate their fire resistance, they were subjected to central compressive load. The significant parameters were determined, such as load, cross-sectional dimensions, concrete strength, and effective heating length. Comparison was made with predicted fire resistance using existing design codes such as Eurocode part 4 and ALT code. It was found that Eurocode and AIJ code's calculation was satisfactory for predicting the CFT cross-section's fire resistance and temperature. In this paper, we have analytically examined the mechanical behavior and fire resistance of these columns under constant axial load. We present a critical review of the currently available material properties for the fire resistant performance of the CFT column. The thermal and mechanical properties of concrete and steel, as previously found by earlier researchers, were used. Based on material properties, a transition of the temperature measured in the concrete's interior was simulated successfully by numerical thermal analysis. Based on the numerical thermal analysis on the CFT columns, a nonlinear stress analysis was carried out taking into account the under-high-temperature behaviors of concrete and steel tube. Comparison between experimental data and analytical results makes recommendations on material properties and the numerical method.