Fatigue assessment of orthotropic steel bridge decks based on strain monitoring data

Orthotropic steel decks (OSDs) are prone to fatigue cracks due to long-term wheel loading with high cyclic stress and unavoidable manufacturing defects. In this study, the stress behavior of the typical connection details in OSD under actual traffic flows is investigated based on local strain monitoring, including the deck-to-rib connection detail, the rib-to-diaphragm connection detail, and the cut-outs detail of the diaphragm. The fatigue performance of the OSD was evaluated based on two weeks monitoring data of hot spot stress. Result shows that the local effect of all the typical connection details is significant under wheel load, and the transverse influence area of each detail is within two longitudinal ribs. The stress level of fatigue vulnerable details was high, the peak value of the cut-outs detail of the diaphragm reached 246 MPa. The fatigue life of the typical connection details of the monitored orthotropic steel deck were all less than 100 years without considering change in the traffic volume, urgent measures should be implemented to improve the fatigue performance. The finite element analysis result shows that an ultra-high performance concrete composite pavement system can effectively reduce the fatigue stress amplitude of structural details. The stress improvement effect of the deck-to-rib connection details was the most obvious, the peak value of the influence line of the weld toe detail of the deck can be reduced to 80-90%, which can effectively eliminate the risk of fatigue cracking of the OSD.