Research On Reconstruction Jacking Technology Of KangYaDi Bridge

With the increase of the traffic discharge on the highway and railway, theraising of vehicle velocity and the growth of wheel load a higher demand waspresented on intensity, rigidity and durability of the existing bridges, and so forth.In our country, most of bridges were built in 1960s or 1970s, which were based onthat time traffic discharge and development planning, so design criterion of thesebridges were very lower. In addition, it was inevitable to bring about cracks,concrete rupture,steel rust, honeycomb and water proof layer failure because someestablished bridges were built by poor construction and maintenance during thecourse of operating period. All abovementioned lead to durability and bearingcapacity couldn't gain to design standard. Maintenance and strengthening must bedone on these bridges.In this paper, the reinforcement scheme of jack the superstructure, which wasapplied to strengthen a prestressed concrete continuous rigid fame bridge withsome quantity faults, such as the rise-span ratio was too low, the clearance underspan was not enough etc. By fitting reasonable external prestressing tendons toensure ultimate bearing capacity of the bridge, to ensure stress reserve of the mainbeam, to reduce effectively principal tensile stress. The paper consists of fourchapters totally. And chapter three is the most important part.Chapter one mainly introduces the study background, the bridge strengtheningmethods commonly used and study content. At present, a lot of research has beendone in maintaining and strengthening bridge in home and out. Specifically, theapplication of external prestressing method and carbon fiber reinforced method areboth talked about. The eight problems in bridge strengthening exist in our countryare pointed. The conclusion that it is necessary to strengthen bridge is drawn.Chapter two introduces the basic principle of finite element method. As aneffective calculation method, its basic point lies in expressing the relation of thedisplacement and internal force on nodes in the formation of algebra. Therefore, theunknown quantities are node displacement, node internal force and displacement.In real practice, the commonly used method is displacement finite element method.And this method is widely used in the analysis of bridge structure.Chapter three takes the KangYaDi continuous rigid frame bridge inTong(Chuan)—Huang(Ling) expressway in ShanXi province. Aiming at that theheight is low, the clearance under span is not enough and etc., the jacking method ispresented. Raising the height of main beam can satisfy the requirement for routeshape after strengthening. In addition, the external prestressing steel is arrangedreasonably to ensure the ultimate resisting capacity. Meanwhile, the stress stockincrease. By comparing the calculation result with the result from experiment, thereal force is obtained when the bridge is jacked. Also, the comparison resultprovides theoretical accordance is provided and the experience is accumulated forconstruction of jacking. In addition, this result provides reference for jackingconstruction of bridge.Chapter four is the summary of this paper. The specific scheme for jackingconstruction is set out by comparing the problems exist in the KangYaDi Bridge.The real-time supervision is carried out in order to ensure that the strengtheningconducted well and completely safely. The longitudinal slope increases from1.068% to 2.6%. Meanwhile, the traffic capacity and safety is improved greatly.However, considering the ability of myself, a lot of work is required to be donefurther. For example, the problem of stress concentration exist in the turning deviceis to be solved. Every girder deck is set up in the top of the pier column. For oneaspect it is to meet the requirement of strengthening using external prestressingsteel. For another aspect, it can also avoid the bending of the external prestressingsteel in one girder deck turning device. Consequently, the stress is concentratedseriously.