Experimental study on residual stress of fire-resistant steel welded box-sections

Residual stress is one of the important imperfections should be considered in predicting the ultimate bearing capacity of welded section columns. Extensive experimental and theoretical study on the residual stress of conventional structural steel (CSS) welded sections have been carried out. In order to provide higher resistance under elevated temperature, fire-resistant steel (FRS) is developed. In view of the different mechanical properties at elevated temperatures and post-fire conditions, the residual stresses may be different for FRS welded boxsections. In this study, six welded box-section specimens are fabricated from 10 mm Q345FR and Q460FR FRS plates with varying width-thickness ratios. The sectioning method is adopted to measure the residual stresses. The magnitudes and distributions of residual stresses of FRS are obtained. A simplified residual stress model for welded box-section in Q345FR and Q460FR steel is proposed. The effects of strength and width to thickness ratio on the residual stresses are discussed. In addition, the residual stresses between FRS and CSS welded box-sections are compared and the reasons for the differences are discussed. The test results show that residual stress to yield strength ratios of FRS welded box-sections are lower than those of CSS welded boxsections.