Fire resistance of composite columns with embedded I-section steel - Effects of section size and load level

This paper presents a numerical study on the fire resistance of embedded I-section composite columns designed according to EC4 Pt.1.2. The objective is to examine the effects of cross-sectional dimension and load level on column fire resistance. Four groups of columns consisting of square cross-section are chosen for study. Their cross-sectional dimensions range from 250×250 to 400×250 mm², respectively. These columns are subjected to axial compression forces and four-face uniform heating. Within each group four load levels are studied, viz., 0.2, 0.3, 0.4 and 0.5. Based on numerical analyses, it is found that under high load levels, columns with small cross-sections fail to meet the fire resistance as suggested by EC4 Pt.1.2. To validate and to prove the reliability of the numerical study, four composite columns were tested under transient heating scheme. The experimental results were validated against finite element (hereafter: FE) analyses. FE predictions of both cross-sectional temperature distribution and structural response during heating agreed reasonably well with experimental data. Column failure times are also predicted using a simple method suggested by EC4 Part 1.2. It shows that EC4 predictions agree very closely with the FE predictions.