The Research Of Safety Evaluation And Analysis Of Fatigue Life About Bridge Crane

With the rapid development of modern science and technology, industrial production is developed continuously toward large-scale, specialized and integrated direction. As an integral aid of modern production, the requirement of crane is growing, the security demands of structure and performance are also increasing. As an important type of crane, the main load-bearing metal structure of bridge crane is the main beam, its common structure is welded beam structure. The main beam contains hundreds of thousands of welds, crack initiation around welds is often resulted from poor welding defects, and propagation of fatigue crack decides the fatigue life of main beam. Therefore, both the research on the laws of propagation process about fatigue crack of main beam according to the theory of fracture mechanics and the reasonable estimate of life about bridge cranes in-service are significant to prevent failure and to guide design, manufacture, use, inspection and management, etc. For bridge crane, the main work in this paper is as follows: (1)Based on full investigation of design standards, system of maintenance, norm of inspection and testing and safety incidents about bridge crane, considering the people (staff), machine (crane), surroundings (environment), supervision(management) and other factors, a fault tree which top event is collapsed bridge was established according to fault tree analysis. Through qualitative and quantitative analysis, the main reasons of bridge failure were summarized, and effective measures to avoid accident were put forward.(2) Statics simulation of main beam which model is QL10+10T×16.5m was done through ANSYS finite element software, dangerous areas on main beam where static stress is relatively large were found, and as a mother model, three sub-models of fatigue crack were established, the cracks from dangerous areas were calculated, the stress intensity factors in the crack propagation process were calculated, and further calculation of the crack propagation life, fatigue life curve was plotted.(3) In order to fully grasp the security situation of cranes, safety evaluation of bridge cranes was done. In this paper, weights were formed by AHP, fuzzy comprehensive evaluation method was adopt to make safety evaluation of bridge cranes, safe evaluation value of the machine was gotten. The corresponding plan of repairment and maintenance for crane was made according to the level of danger, integrity management was achieved.