Steel Bridge Fatigue Life Design

Bridge design many years ago, problems in construction and service do not be considered all. It leads to some questions such as use function, structure disease and low resistance, high enlistment maintenance costs etc. And some economic and social problems also appear because of these. In such situation, it needs some new design idea which can include all of the problems in construction , service and management, that's "whole life design".This paper is the important ingredient of "Bridge Steel Structure Compent and Cable System Life Circle Design Guide Rule Study" which is the subsidiary subject of "Bridgework Life Circle Design Theory and Method Study" that belongs to Nation west traffic construction science and technology item. The paper is established in the bridge steel structure compent. Major reseach is the fatigue of bridge steel structure.In the article, based on "whole life design", it brings forward variable assurance ration in fatigue equations, so that different assurance ratio can be used according to the difference of structure replaceable and significance .Fatigue in steel structure of bridge is one of the main factors which affect durability. Code for design on steel structure of railway bridge (TB10002.2-2005) based on many experiments has some property such as advancement, applicability and reliability. It can show our manufacture craft and level, and the real condition of bridge structures.Compare with the above code, Code for design on steel and timber structure of road bridge(JTJ025-86) has dropped behind much more. The code adopts to ratio of stress as fatigue control factor is quite different from new theory, And it can't reveal real condition of structures. The result of fatigue calculating seems to unsafely. That's to say, The code should better change.The article bases on the experiments done by railway institute for a long time and new fatigue research theory inside and outside, Put forward a set of optimum methods for structure design. The expectation is to make a guide for designers.The results of research in the article are shown by design rules and calculating demonstration, It expects to serve for designers.