Structural Behavior Analysis Of Bridge Suspenders

Bridge suspenders are mainly used in through-arch bridges,half-through arch bridges and suspension bridge. In the recent twenty years,through-arch bridges and half-through arch bridges with suspenders developed rapidly.The suspenders are important force transmission components,which have characteristics of small size,multiple component parts,sensitive to many factors such ascorrosion and fatigue,and the operation state of suspenders and its components is fairly complex.It works normally or not,affects the operation safety and lifetime of the wholebridge.However,the current bridge design theory has not kept pace with the development of the bridge,there is no uniform and scientific standard for design criterion of the suspender,the service injury,safety criteria,life prediction,removal and replacement scheme and so on,and most of the past engineering practice is based on the subjective judgment of the designers.In addition,the bridge designers paid little attention to the force of suspenders.They usually adopt a safety factor to control itsmaximum stress in the design,but ignored the control of fatigue and corrosion problems.As to the factors affecting fatigue of suspenders and its changes law,there are almost no comprehensive and systematic researches,so the suspenders'breakage occurred frequently.Therefore,on the basis of referring and summarizing the having achievements and present status,this article takes a certain half-through arch bridge as the background.And structural behaviors of suspenders were calculated and analyzed.The main contents and conclusions are as follows:①Static and dynamic analysis of suspenders.On the one hand,that the simply supported beam model is incorrect and model of continuous beam with elastic supports should be adopted is explained.Also,influence of shrinkage and creep of concrete on suspender is analyzed.On the other hand,influence of bridge vibration and connection ways of suspenders with ribs and lateral beams on suspenders is introduced on the basis of method to calculate vibration frequency of suspenders.Besides,basis theory of FEA method is introduced in this paper,with which the Midas/Civle model of bridge example is built.②Failure analysis of suspenders.Through the analysis of the widespread dilapidation phenomena of the hangers,combining the construction features of the hangers of the steel pipe concrete arch bridges,a conclusion is reached in the thesis that corrosion and fatigue are the most important causes for the dilapidation of the hangers.The improper protection measures of the hangers may lead to their corrosion and dilapidation,and the fatigue due to the stresses caused by the live loads could mainly explain the dilapidations.Protection measures are proposed in the paper.③Fatigue analysis of suspenders.Fatigue is another reason to damage of suspenders,so damage mechanism of suspenders including theory and method of anti-fatigue design is introduced in this paper.Also,the same as anti-fatigue design code of cables,it says stress scope is the key to control fatigue of suspenders. Through the discussion of the range of safety factor,we think that the current design can not guarantee the security of suspender in service,and we should establish an appropriate design theory and method as soon as possible.④Fatigue factors analysis of suspenders.From the perspective of structural design,we analyze and compare the factors that affect the suspender fatigue under load, and obtain structural design methods that are conducive to improve suspender fatigue.