Useful Structural Life Assessment of Dockside Container Cranes

What is to be gained by a useful structural life assessment of older cranes? What is "useful life?" The useful structural life is the remaining time the crane can be operated with an acceptable risk of failure. When first asked to consider acceptable risk, the usual response is an acceptable risk is no risk. Unfortunately, all structures have a reliability of less than 1.00. For cranes, the most common acceptable risk of a single structural detail failing is about 1 in 50, using the damage tolerant design philosophy. The consequences of the failure of one detail may be limited with periodic inspection. This paper presents the methods used to develop a structural inspection program and to evaluate the useful structural life using statistical analysis and the principles of fracture mechanics.