Influence of Internal Pressure on Hollow Section Steel Members in Fire

Abstract

Structural steel hollow section members are extensively utilized in civil engineering due to their excellent mechanical performance, favourable geometry for corrosion protection, and aesthetic appeal. Degradation in material properties of steel and thermal expansion at high temperatures must be regarded in designs for fire situations. The closed inner space of hollow sections presents challenges at elevated temperatures. The present study examines the effect of expanding air on the stress state in section walls of hermetically sealed circular and rectangular hollow sections. The effect of the gas pressure is calculated analytically and numerically. The pressure of the expanding air may substantially reduce the capacity of a tubular member. The influence on resistance depends on temperature, volume of the air in the tubular member, and geometry of the hollow section. The results of the study indicate that rectangular hollow sections with relatively large width-to-thickness ratios are more sensitive to internal pressure than circular hollow sections. The temperature range where the adverse effect of internal pressure occurs can include realistic critical temperatures in practical design and therefore deserve special attention to ensure the required safety.