Study On Fatigue Reliability And Safety Control Of Steel Structure Crane In Service

Fatigue failure is one of the main failure models when the engineering structures are beard under cyclic loading. 80%-90% destruction on steel crane structures in industrial building due to the fatigue. There has very important practical value to study the statistic character of fatigue load on steel crane structures and of fatigue resistance on all kinds of structural joints and to analysis the fatigue reliability of structural detail, which can be used to fatigue safe control.The fatigue reliability theory and fatigue safe control applications on steel crane structures in service are studied based on the structural reliability theory in this paper. The major contents are mainly summarized as follows:1. The main destruction model of steel crane structures in service is summarized, the destruction reason is analyzed, and the main procedure of fatigue safe control on steel crane structures in service is established based on many engineering investigation and formerly engineering appraisal instance.2. Statistic analysis on fatigue load effect and equivalent stress range of steel crane structures in service is carried out. The stress range distribution in whole life is deduced by the spot measurement little sample stress-time process. Meanwhile the statistic analysis on the fatigue resistance process is conducted, according to fatigue data of all kinds of structural joints in domestic and overseas, which is foundation with, establish the fatigue reliability model.3 . The crane load and fatigue strength are regarded as stochastic process, the fatigue dynamic reliability based on limit stress model and fatigue dynamic reliability based on accumulation damage model are established on the base of statistic analysis the fatigue load and resistance. The two models are identical in essence.4. Fatigue safe control assessment method on steel crane structures in service is put forward based on fatigue dynamic reliability. After investigating and summarizing many engineering usage and appraisal. Based on the Miner accumulation damage model, in a fatigue reliability point of view, the remain fatigue life assessment equation in the (Technical Specification for Inspection, Assessment and Strengthening of Steel Structures)) (YB9257-96) is analyzed, and the probabilistic meanings of the additional safe factor is proposed.5 . The strategy on repair and reinforcement on steel crane girder structures in service based on fatigue dynamic reliability is analyzed in the paper. Considering the benefits of repair and the long-term economic affection after repair and reinforcement, using the fatigue dynamic reliability as constraint condition, thinking of that the sum of benefits of repair and reinforcement as object function, the optimization model is put forward. Then it is used to an certain crane arc ends repair an reinforcement. It shows that the method and the results can be used for designer, capital construction manager and researcher reference.6> The statistic parameters of load effect and resistance on fatigue reliability are studied in the paper. According to statistic analyzing of the real data from spot and the old test data, the fatigue reliability is calibrated on 8 details, which are provided in the code, by first order second moment (FOSM). The target reliability beta and partial factor equation are proposed according to the above results. A certain crane truss girder is analyzed by FEM method, and the results of FEM are compared with the test results. The fatigue strength of bottom chord node board, which is sensitivity to fatigue, is calculated by FEM method. Fatigue strength checking computations are carried out for this crane. It is incline to danger when fatigue strength of node board is calculated by pervasion angle in code.The research work is supported by National Science and Technology Ministry Society Welfare Project. "Safe control technique study of Industrial building based on the structural reliability...