Fatigue life evaluation of existing highway reinforced concrete bridges

Generally, fatigue has not been considered as a key problem in the design of reinforced concrete bridges. Until the 1960s, reinforcement was mild steel and the stresses permitted in the steel bar and the concrete were such that fatigue and fracture failure was believed to be impossible. With the developments of reinforced concrete structures, higher working stresses were permitted and, in particular, high yield reinforcing bars were introduced. In recent years, some studies showed that fatigue could occur in reinforced concrete structures in combination with other causes of deterioration. In the past ten years, considerable increases in traffic volume and wheel loads have caused obviously fatigue damage in existing highway reinforced concrete bridges in China. Some highway reinforced concrete bridges were damaged seriously, leading to the whole bridge collapse sometimes because of overloading and oversize trucks. So how to evaluate the fatigue safety of existing reinforced concrete bridges is an urgent problem in China. In the current paper, the assessment models of existing reinforced concrete bridges based on S-N curve and linear elastic fracture mechanics (LEFM) were proposed. Furthermore, the assessment methods based on S-N curve and fracture mechanics using in-situ monitoring data were applied to a case study bridge.