Investigation on Postfire Residual Capacity of High-Strength Steel Columns with Axial Restraint
Guo‐Qiang Li, Jiarong Miao, Linxin Song, Wenyu Cai, Jian Jiang
Abstract
This paper experimentally and analytically investigates the fire and postfire behavior of axially restrained high-strength steel columns. Tests on the buckling behavior during heating as well as the residual load-bearing capacity after heating are first conducted on the column specimens made of Grade Q550 steel with a yield strength of 730 MPa. A numerical model is established and validated against the test results, and parametric studies are conducted with influencing factors including the maximum temperature, load ratio, slenderness ratio, and steel grade. A simplified calculation method is proposed to determine the residual capacity of restrained high-strength steel columns. The experimental results show that restrained high-strength steel columns buckle at a low temperature of about 300°C. The postfire residual capacity and axial stiffness of the columns are significantly reduced to a level of 55% and 32% of its initial values, respectively, due to the presence of a residual bending deformation. The numerical results show that the residual strength decreases greatly if the maximum temperature of a column is higher than its buckling temperature. The axial stiffness ratio and slenderness ratio have a significant influence on the residual capacity of restrained high-strength steel columns at buckling temperatures, while the axial load ratio has a significant influence at critical temperatures. However, the steel grade has little influence on the residual capacity of restrained high-strength steel columns.