Study Of Bridge Steel Structure’s Corrosion And Fatigue Stress

With the rapid development of our country’s economy and traffic, bridge construction isbooming. Steel bridges are often the first choice because of its light weight and strongspanning ability. But bridges are often located in the place of complex environment and badclimate. As a result of long standing effect of the surrounding environment, bridgesunavoidably have corrosion damage, which affect its normal usage and safety. Thus, it leadsto a research about steel bridge corrosion and fatigue life that can’t be ignored and must besolved. The study of steel bridge corrosion and fatigue stress that considering corrosion canstrengthen bridges’ corrosion protection, prolong the service life of security, protect andreasonably use all kinds of resources. It provides reference for the corrosion protection,reinforcement of the bridge and has a very important practical significance in the bridges’normal operations and avoiding accidents.This paper discusses the corrosion environment and the law of development of steelbridges based on the forms and characteristics of atmospheric corrosion. Then, this paperstudies the effects on fatigue life of the two most common corrosion forms: pitting corrosionand uniform corrosion, starting from the relation between stress amplitude and corrosion byutilizing the general finite element software ANSYS. The study of pitting corrosion isbased on a Highway Bridge and the study of uniform corrosion is based on samples that meet《National standard of Tensile specimen》 GB/T228-2002. The main contents are as follows:Firstly, for uniform corrosion, the finite element model of orthotropic steel deck isestablished by software ANSYS. Select the foci that need to fatigue calculation and get thestress history of the foci according to the survey fatigue load spectrum. Taking different timeto count and fitting each stress cycle’s stress amplitude changing curves in each focus andeach vehicle based on rain flow counting method. Then we can get stress amplitude changingfactors from these stress amplitude changing curves. With the growth of the time, stressamplitude changing factor is larger and the fatigue life decrease.Secondly, for pitting corrosion, the pitting corrosion morphology can be simplified as asemi-ellipsoid. Set up single corrosion pit’s multiple finite element models of different pittingcorrosion morphology and find that pitting corrosion morphology has a larger influence onstress concentration factor. Moreover, set up multiple finite element models of samemorphology, different numbers and different hole center distances. We can find that stressconcentration factor of single corrosion pit is bigger than multi-corrosion pits. The more the number of corrosion pits there is, the smaller the stress concentration factor is, and the widerthe spacing between the corrosion pits, the bigger the stress concentration factor is.