吊臂是起重机的重要部件，其设计的好坏将直接影响起重机整机的性能和经济成本。吊臂除了应保证起重机具有良好的性能而必须具备足够的强度、刚度、稳定性外，还必须力求轻巧。吊臂自重过大，材料利用率低，是伸缩式吊臂起重机向大型化发展的主要障碍之一。降低自重不但可以节省原材料、减少劳动量，而且还可以减轻机构的负荷和承载结构的造价、提高起重机的灵活性与起重特性。因而探索科学、合理的设计方法是现代起重机设计中必须解决的问题。本论文首先从科学设计方法的角度指出现行的各种设计方法的优点和不足，在起重机伸缩式吊臂设计中，从常规优化设计出发，根据起重机所受载荷的随机性和传统强度判据的模糊性，在优化设计中引入可靠性和模糊性，首次将可靠性、模糊性与优化设计相结合，对吊臂提出了一种更新、更合实际的设计方法——模糊可靠性优化设计；利用概率统计和模糊数学等知识，建立了19个设计变量、135个约束条件组成的，并以吊臂重量最轻为设计目标的箱形伸缩式吊臂的模糊可靠性优化模型。同时用Motel-Carlo模拟法求未知分布函数应力的可靠度，用水平截集法将模糊优化转为常规优化，提出了伸缩式吊臂模糊可靠性优化模型相应的求解策略，并在MDOD的基础上用FORTRAN语言编制了一套实用、准确、通用性较强的伸缩式吊臂的模糊可靠性优化设计程序。论文并对QTJS160铁路起重机的伸缩臂进行了实例优化，提出了优化方案以供参考。

As one of important component of crane ,whether jib is designed well or badly will influnence directly on performance and cost of whole crane .Jib need hanker after handiness besides having enough strength ,rigidity ,and stability to ensure whole crane having good performance .Jib’s self-weight too high and material’s useful rate too low are one of primary obstacles of telescopic jib crane developing to large-scale crane . Self-weight lowered don't only save on raw material , decrease amount of labour , but also lighten burden of machanism ,lessen costs of bracing structures . Since what search after scientific and reasonable designing methods imminently need solving for modern crane design. This paper firstly point out merits and defects of using design methods now from angle of scientific design method .In crane telescopic jib designing ,in order to be very consonant with practicalness the Fuzzy Reliable Optimization that combines fuzzyness with reliable, optimal design for the first time is applied, owing to taking randomness of practical raising weight and fuzzyness of stress-strength interferotheory into consideration on basis of conventional optimal design, and make use of probability- statistics and fuzzy mathematics etc, establish fuzzy reliable optimal model of telescopic jib ,with 19 design variables and 135constraint conditions , by taking minimum weight of telescopic jib as object .In the mean time Motel-Carlo stochastic simulating method is used to solve reliability of stress that ranged function is unsuspected , λhorizontal intercepted sets is applied to transform fuzzy optimization into conventional optimization ,and put forth homologus solving strategy. and write a set of utility program for the model in FORTRAN on basis of MDOD. Furthermore ,the paper example the design of telescopic jib of 160t Railway Rescue Crane , and provide optimal solution so as to reference.