Study On Condition State Assessment Of Cable-stayed Bridge Based On Fuzzy Inference

Cable-stayed bridges are always the first chioce of a long-span bridge, and bridges are the throat of highway transpotation system. Due to the effect of environment and the increasing traffic and vehicle load, the functions of great amount of existing bridges degenerated, so the reinforcement and maintenance of the existing . bridges are very hard. It has great social significance and economic values to evaluate the load-carrying capacity of existing bridges, and helps to ensure the security of existing bridge structures, decide the strategy of repairing and maintenance scientifically, and assure the traffic artery smoothly.The paper introduce fuzzy inference into cable-stayed bridge assessment and present the method and practice application research of condition state assessment of a cable-stayed bridge as follows:1 Give a complete assessment model to evaluate the state of a cable-stayed bridge based on AHP(the Analytic Hierarchy Process), and the model is made up of four part which is main girder,cable,main tower and accessory structure.2 According to the assessment model, we decide the content for evaluation and the judgements for each evaluation part, then we give a criterion for each judgement according to the standard or regulations in bridge domain.Sigmoid membership function is used in this paper, and we determine the parameter by the criterion of each judgements.3 Based on the opinions of expert in bridge domain and combined with theoretical analysis, we established the fuzzy inference rules to the evaluation targets, and the rules are expressed by two different ways for the different ways of inference.4 Two different ways are used in the fuzzy inference process,one is inference computation based on fuzzy rules,the other is fuzzy-neural network.The study on the condition state assessment of existing bridges is becoming ahot problem worldwidely. When we adapt the fuzzy inference method to the condition state assessment of bridge , reasonable rules is of great importance ,the result of assessment is determine by the fuzzy rules .But there is not much rules avaliable in the domain of bridge assessment .The paper give the rules based on the experience of bridge expert, so we only give a explain of the condition state assessment of accessory structure, then we give a condition state assessment of the cable in Ba Dong Yangtze River as an example.