Modelling a steel-plate girder bridge strengthened with carbon-fibre reinforced polymer

This paper reports on a numerical study into the crack-dependent behaviour of a steel-plate girder bridge strengthened with carbon-fibre-reinforced polymer sheets. Progressive cracking, which represented fatigue-induced damage, was simulated from up to 10% of the girder depth. Finite-element analysis was used to evaluate the performance of the control, damaged and strengthened cases subject to standard US highway fatigue loading. The efficacy of polymer strengthening was also examined from a strength perspective, using the load factor rating method and the load and resistance factor rating method. Localised fatigue cracking caused a stress concentration along the girder and its progression rate was related to the degree of web fracture. The damage of the tensile flange was more influential in reducing the flexural capacity of the girder relative to damage of the web. The strengthening decreased the stress ranges, thereby increasing the fatigue life of the girder, and enhanced the maximum average daily traffic capacity. Reliability modelling indicated a transition in failure rates before and after 3% cracking in the girder, supporting the extended functional time resulting from strengthening.