ABSTRACT
A large span cable-stayed bridge in China adopts a flat steel box girder for its main section. The bridge has been affected by heavy-duty vehicles and huge traffic flow for a long time since it began operation. During the regular inspection, it was found that the steel box girder had a budding phenomenon of fatigue cracking, especially the cracking of fillet weld between U rib and roof. Welding repair technology is a common means of steel structure repairing at present. This method has an adverse effect on the toughness of repeated welding positions, causing sensitive points of fatigue cracking under load and affecting safety of the structure. In the maintenance project of this bridge, non-destructive repair technology was attempted, and the fatigue cracks were treated by the technology of sticking steel plate. The shell-spring model was used in this study to analysis the mechanical properties of the U-rib after steel was bonded. The theoretical results show that the appropriate thickness of the bonded steel can reduce the stress concentration at the end. The effects of temperature, vibration and other conditions on curing effect were obtained in the process test of structural adhesives used for bonding steel. The static loading test of model beams was carried out, and results show that the bonded steel plate has good connection effect with the base material, and the synergistic force performance was stable.Based on the above research results, existing diseases were treated under effect monitoring. The current monitoring results show that the local stiffness was improved after the steel was bonded, and the stress amplitude under the random vehicle flow was reduced. In order to verify the long-term performance of the method, the reinforcement position will be continuously monitored in the later stage.
