Effect of creep on behavior of steel columns at elevated temperatures

Purpose This study focuses on the impact of creep on the behavior of steel columns at elevated temperatures, considering both loading rates and creep buckling. The loading rate directly influences the duration of loading, while creep buckling illustrates how the critical buckling load depends on load duration. The capacity curve of the steel column is obtained for temperatures ranging from 400°C to 900°C, with loading rates varying from 2.5 to 0.10 mm/min. Additionally, the stress distribution across the cross-section of the column is analyzed. Design/methodology/approach A set of comprehensive experimental data at elevated temperature, including results from tension, buckling and creep buckling tests, is employed. The data from fast tension tests are used in the current study. Also, accurate coefficients for the creep model are obtained. As a result, a behavioral model for ASTM A992 steel has been developed, which accurately predicts the performance of steel columns at high temperatures. The effect of loading rate on the stress-strain curve of steel was determined and compared with Eurocode and NIST models. Additionally, parametric analysis is performed, specifically focusing on creep buckling of steel columns across a temperature range of 400°C–900°C. Findings In this study, a behavioral model for ASTM A992 steel has been developed, accurately predicting the performance of steel columns at high temperatures. The phenomenon of creep buckling in ASTM A992 steel columns has been investigated at temperatures ranging from 400 to 900° and compared with Eurocode standards. Reducing the loading rate in steel tensile testing can lead to a decrease of up to 40% in the tensile strength of steel at high temperatures. If a fire lasts for up to 200 min, the buckling load of the steel column can be reduced by up to 50%. Originality/value This study assesses the impact of creep on steel columns using unique experimental data obtained from steel samples. The data from fast tension tests are utilized in this study, effectively eliminating errors associated with creep effects. The behavioral model of steel is derived from these fast tension tests, and specific coefficients for the creep model are obtained. The proposed model has been validated through both fast and slow tensile tests of ASTM A992 steel. Additionally, this model has been compared with several commonly used high-temperature steel behavior models. The ability of these models to predict the buckling load of steel columns has also been evaluated.