Effect of local damage on the behavior of a laboratory-scale steel truss bridge

This paper presents an investigation into the performance of a steel truss bridge subjected to local damage. An experimental program with 16 damage scenarios is conducted to study the behavior of damaged truss systems. A three-dimensional numerical model is developed to predict the test results. Static and dynamic responses of the damaged trusses are compared with those of the control. Various technical aspects are studied, including damage quantification using a damage index, load rating, variation of strain energy, modal analysis, and structural safety based on simple reliability theory. Service performance of the truss bridge is significantly influenced by local damage (i.e., damage index >0.5) and the load-carrying capacity is exponentially reduced with the increased damage index. A high mode shape such as the 4th mode is of use to diagnose local damage in the truss system. The global safety index derived using deflection characteristics is an indicator to indirectly detect the presence of local damage in the system. Stress redistribution among the constituent truss members is found to be insignificant, except for those adjacent to the damage. The global safety index of the system based on deflection characteristics is an indicator to diagnose the presence of local damage. The need for developing a repair method that can address the global redundancy of a damaged truss bridge is highlighted.