FATIGUE SERVICE LIFE EVALUATION OF EXISTING STEEL AND CONCRETE BRIDGES

In recent years, traffic loads and vehicle speeds on both existing steel and concrete bridges have increased to provide fast and sufficient transportation service in China. Chinese government and bridge engineers are paying more attention to the structural fatigue life, service safety, maintenance intervals and the ability to. improve capacity of such infrastructure. To study evaluation methods using modern technologies to achieve economical maintenance and extend the sustainable service life, a deterministic evaluation approach was proposed in this paper based on investigation of linear fatigue-damage accumulation theory and fracture mechanics, in which the fatigue failure behaviour of existing steel and concrete bridges was reflected. According to the stochastic fatigue failure mechanism of existing bridges, the member fatigue reliability assessment models were proposed using probabilistic fracture mechanics. Furthermore, based on a Monte-Carlo method, a fatigue reliability analysis program was developed to calculate member fatigue failure probability of existing bridges. The deterministic and probabilistic assessment methods proposed in this paper were applied to evaluate typical existing steel and concrete bridges. According to assessment results, the deterministic and probabilistic remaining fatigue life, safe inspection intervals and maintenance strategies were determined, which can avoid fatigue failure accidents and reduce the life-cycle cost of these bridge structures.