Bridge Crane Metal Structure Residual Fatigue Life Reliability And Sensitivity Analysis

As the skeleton of a bridge crane, metal structure is the main bearingmechanism of work bodies, power equipment, control systems and other parts ofa bridge crane. Its fatigue residual life determines the life of the entire bridgecrane, and also determines the reliability and security of a bridge crane.Meanwhile, with the bridge crane developing towards large scale, heavy hauland operating frequency, the reliability issue of metal structure fatigue residuallife is becoming more and more prominent. The specific impact data of fatigueresidual life parameters affecting the reliability needs to be obtained for areference, when metal structure is faced with safety assessment and reliabilityanalysis. However, bridge crane metal structure fatigue residual life based onfacture mechanics is vulnerable to the initial crack size, the critical crack size,stress ratio, stress range and other parameters. Each parameter can have certainrandomness, and different parameter can have a different impact on thereliability of fatigue residual life. Thus, through reliability and its sensitivityanalysis for bridge crane fatigue residual life, the data of parameters’ impact onreliability can be obtained, which has an important practical significance andwork value.Based on equivalent fatigue reliability test of bridge crane metal structure, thispaper assesses the fatigue residual life according to facture mechanics, takes therandomness of the initial crack size, critical crack size, stress ratio, stress rangeand other parameters into account, establishes the fatigue residual life reliabilitymodel for bridge crane metal structure, and calculates the reliability and itssensitivity of fatigue residual life. Through reliability analysis, study the fatigueresidual life parameter’s influence on reliability, and offer some suggestions forthe next safety assessment and reliability design.Specific research mainly includes the following aspects:1) Based on equivalent fatigue reliability test of bridge crane metal structure,explore the relationship between fatigue residual life of metal structure andreliability, and explore the influence factors of fatigue residual life. 2) Based on the theory of fracture mechanics, according to Forman formula,establish the fatigue residual life assessment model of bridge crane metalstructure with constant loading, considering the impact of stress ratio.3) Establish the fatigue residual life reliability limit state equation for bridgecrane metal structure, and select the distribution information of fatigue residuallife parameters.4) Based on Monte Carlo method, calculate the reliability of bridge cranemetal structure fatigue residual life reliability model, obtain the reliability index,and analyze the reliability status of bridge crane metal structure under thecurrent circumstances.5) Based on Markov chain Monte Carlo method, calculate the reliabilitysensitivity for bridge crane metal structure fatigue residual life reliability model,and get the dimensionless local reliability sensitivity of basic variabledistribution parameters. Through sensitivity results analysis, study the variabledistribution parameters’ impact on fatigue residual life reliability. Sort the localreliability sensitivity results, and determine the more important distributionparameters for metal structure fatigue residual life reliability.6) Based on local reliability sensitivity results, calculate the reliabilitysensitivity and its factor of fatigue residual life parameter. Get the parametersorting of impact on reliability, and determine the more important parameters formetal structure fatigue residual life reliability.7) Stress range has a more prominent impact on reliability, but it is so randomthat its distribution parameter information is always incomplete. Consideringthis, analyze the global reliability and its sensitivity respectively for stress rangemean and standard deviation based on Monte Carlo method and Maximumentropy method. Through global failure probability function, determine the trendof failure probability when stress range distribution parameter varies in itsdefinition interval. Through global sensitivity function, determine the trend ofstress range distribution parameter’s impact on reliability when stress rangedistribution parameter varies in its definition interval.