Research On Safety Assessment Of The Bridge State Based On The Uncertain Analytic Hierarchy Process

Long-span bridges are the hinges of traffic system and play an important role in national economic and society. With the bridge span increasing, the research of the safety and durability of long-span bridges has become the focus of bridge engineer. With the development of bride analysis theory, structure material and building technique, the span of the cable-stayed bridge is getting longer and longer. The special mechanics behavior and the superiority in construction make the cable-stayed bridge has a widely use in long-span bridges. But, with the growth of the span, the safety is becoming more and more important. How to evaluate the safety of the cable-stayed bridge under the permissibility of economic and technique condition is an important and urgent task. To this problem, this dissertation gives a deep study on the safety evaluation of the cable-stayed bridge based on the existing safety evaluation methods. The main achievement of this dissertation are briefly mentioned as follows:The paper first overview the state of the methods of bridge assessment, and probe into its connotation and developing direction about the safety evaluation of bridges, and especially points out that an uncertain type of analytic hierarchy process (AHP) method can be applied in the synthetic assessment and management of bridge. Give a complete evaluation model to evaluate the safety of a cable-stayed bridge based on AHP (the Analytic Hierarchy process), and the model is made up of three parts which are the load bearing, the durability damage and the bridge condition. Further more, give it's complete index system according to the practice of the cable-stayed bridge. And we divide the state of the structure or structure members into five categories: good, fairly good, slightly bad, bad and dangerous. Interval number judgment matrix and the corresponding method of calculation weighs are introduced in the uncertain AHP because of the uncertainty and fuzziness of bridge assessment, so the AHP is extended to the uncertain type of AHP. The group decision-making is applied in the synthetic assessment, and the credit degree is put forward to considering the expert's appraisal level. The principle of set-valued statistics and the fuzzy gravity center based decision theory are put into a new method, and are applied in the uncertain type of AHP. At last, we give a safety assessment in Ba Dong Yangtze River as an example. Input the inspection data to the sigmoid membership function and get a fuzzy set, then the fuzzy inference start according to the fuzzy rules.Now the safety evaluation of bridge is becoming the hot problem in the research of bridge engineering. The main purpose of this paper is the study of the safety evaluation methods for bridges. In the evaluation field of safety of bridges, there are still many works need to be further studied, for example: how to define the characteristic indices and grade standards, how to determine the weights of indices in economic analytic methods.