The Research Of Off-Loading Effect And Application In Project Of Prestressed-Steel Box Arch Method

Arch bridge has its own technical advantages and is widely adopted in the world.It is so widely adopted because of its great weight bearing capacity and long span of each arch.Besides,it is ecnomic and doesn't need too much maintenance costs.What's more,the material is easy to get on the spot and it is good-looking in appearance.However,for both environmental and artificial factors,the structure of these arch bridges are universally destroied to some extent,which have histories of tens of years,or even hundreds of years.And this has severely weakened the carrying capacity of these bridges.Therefore,in order to make sure of the smooth traffic system,it is an urgent issue to reinforce and maintain these old bridges.The reinforcement of old bridges has many advantages compare with reconstruction, either from the aspect of engineering economy or social benefits.Hence,researching on the reinforcement of old bridges is of great theoretical and actural significance.The paper generally reviewed the methods of bridge inspection and reinforcement at first.On the basis of integration and analysis of some of bridge reinforcement method,the paper put forward a new arch bridge reinforcement method,that is steel reinforcement bottom up arch method.This paper gives a detailed introduction of the theoretical basis,construction procedure and practices of this method.The paper discussed the effect of off-loading and cooperation with different bottom thrust,on the base of that The paper bring out the reasonable range of bottom thrust,And then,give out the example of Fangfan Bridge which was reinforce in this method.Finally,this paper gives a modeling analysis of the situation before and after the reinforcement,by adopting the finite element software.Combined with the analysis and comparison of inspection data,the paper analyses the impact of reinforcement when the bridge is applied to different thrust.The analysis method of finite element medeling offsets the shortage of the traditional inter force computation,provides a credible quantitative analysis data for the reinforcement and reconstruction and offers a foundation for working out a suitable scheme for reinforcement.This method allows the added steel arch to stand without adding the weight of the original structure.Besides,when doing the work of reinforcement,one does not need to change a lot of the original sturcuture,so this way of reinforcement will not do any harm to the original structure of the bridge.Inflicting some thrust to the steel-box Arch means to remove part of the dead load of the original structure,and this helps to reduce the stress level of primary arch rib.However,too much thrust will further damage the primary arch rib and does no good to it.Thus,the key point in adopting this method is to work out the level of thrust.And finite element analysis palys a instructive role in working out the level of thrus.The practice of this bridge provides a reference for the reinforcement of this kind of bridges.