Experimental Investigations of the Rotational Stiffness of Single-Sided Fillet Welds

Current design codes do not include a design approach for single-sided fillet welds subjected to bending. For this reason, and the expectations on the low bending resistance of single-sided fillet welds, fillet welds are generally welded from two sides. However, this is not always possible. Due to the geometric constraint of non-accessible hollow boxes, longitudinal fillet welds cannot be executed from two sides. This type of cross-section is often used in steel and steel-composite bridges with short and medium spans. It was found that these welds are subjected to bending caused by internal pressure fluctuations. This bending load is considered in the German National Design Regulation. The regulation was developed by simplified assumptions leading to an increase of the weld thickness of single-sided fillet welds. In this study, investigations regarding the bending behaviour of single-sided fillet welds are carried out. Therefore, specimens with single-sided fillet welds are subjected to a bending load. The results are compared to simplified analytical load-bearing capacities. It was found that the load bearing capacity of single-sided fillet welds is underestimated by the simplified calculation methods. The German regulation's increase of the weld thickness of single-sided fillet welds results in an uneconomical design of the welds.