The influence of diaphragm stiffening on welded tubular nodes in arch bridges

A tubular arch bridge is prone to fatigue damage, particularly in the presence of varying traffic loads. The intersection of various tubes at the nodes of a tubular structure constitutes a radical transition of the geometry of the main tube. Due to geometric discontinuity, stress concentrations are introduced at the nodes. Because the nodes are welded, other stress concentrations add up to the former ones, particularly near the weld toe of the joints. By introducing internal diaphragms inside the main tube, the stresses in the weld toe can be reduced. This paper focuses on decreasing the hot spot stresses at the weld toe, as a function of the diaphragm location. By lowering the stresses at the weld toe, the fatigue resistance of the tubular arch bridge will be increased. To calculate these so- called hot spot stresses, accurate FE-models are being be assembled.