Experimental Investigation on the Post-fire Behavior of Fillet Welds in the Welded Connections

Abstract

The post-fire behavior of welded connections is defined as the decrease in strength after exposure to a complete heating and cooling process. This change in strength is the key aspect for estimating the structural performance of welded connections after exposed to fire. To address this issue, this paper presents significant results of an experimental program investigating the effect of the heating and cooling process on the structural response of fillet welds subjected to different load angles. Eighteen experimental tests are carried out to examine the residual behavior of fillet welds for three different welded lap joint configurations after exposed to fire temperatures. The lap joints are categorized as longitudinal, inclined, and transverse, where the angle between the axis of the fillet weld and the direction of the applied load is 0°, 45°, and 90°, respectively. To examine the post-fire response of the three welded lap joints, the lap joints are exposed to a complete heating–cooling cycle and then loaded until failure. The post-fire tests were conducted at elevated temperatures ranging from 400°C to 900°C with 100°C increment and then cooled back to ambient temperature of 20°C prior loading. The residual responses are characterized as load–displacement characteristics after exposed to elevated temperatures. The results showed that the strength of the fillet welds for all load angles decreases as the temperature of the post-fire analysis increases. The decrease in fillet weld strength reached approximately 25%, 22%, and 27% of its initial strength for 0°, 45°, and 90° load angles, respectively, after 900°C post-fire temperature exposure. This study provides preliminary data that can support the development of design guidelines of welded connections during and after fire exposure.