Fatigue behaviour of orthotropic steel bridge decks with inner bulkheads

Tests on a full-scale orthotropic steel deck (OSD) specimen were conducted to investigate the effects of inner bulkheads set inside the U-ribs on the static and fatigue behaviours of the OSD. The total length and width of the OSD specimen are 5 m and 2.24 m, respectively. It contains three longitudinal floorbeams and four transversal U-ribs. U-ribs with and without inner bulkheads are symmetrically arranged in the cross section of the specimen. Finite element (FE) analyses on the OSD specimen model and sub-models were conducted to further study the effects of the inner bulkhead design and different bulkhead shapes. Results of the test and corresponding FE analysis of the specimen showed that inner bulkheads can be used to improve the fatigue life of the OSD. Meanwhile, fatigue cracking in the rib-to-bulkhead details was introduced by installing the inner bulkhead. Results of the FE analysis of the sub-models showed that the distance from the bottom edge of the inner bulkhead to the tip of the floorbeam cutout affects the stress state of the rib-to-floorbeam connection weld significantly. Additionally, the bulkhead shape affects the hot spot stress of the weld toe of the rib-to-floorbeam connection weld significantly. Thus, proper bulkhead shape should be determined by considering the specific stress distribution of the rib-to-floorbeam connection area.