| Arch bridge is a common type in highway engineering and it has a long history in our country. As the arch is the main structure to resist stress, it can make full use of masonry materials whose tensile performance is poor and compressive performance is good. This kind of bridge has lots of advantages such as lower cost, simpler structure, and more mature construction technology. There are many types of arch bridge for example reinforced concrete arch bridge, double-curvature arch bridge, truss type hybrid arch bridge and the concrete-filled steel tubular arch bridge. Since piers shall inherit horizontal force as well as vertical force, they need much higher requirements for foundations. That's why there are a large number of arch bridges in western mountainous area. With the rapid development of national economy and the increase of traffic transportation, traffic density and vehicle load, some age-old bridges can not meet the requirements of normal operation. Because of the lower design standard, a considerable number of bridges have become dangerous. Vault construction as free end has the maximum internal forces and is the most concentrated area. The crown section is also the main part which may be destroyed during normal operation. Vault strengthening is a bottleneck in arch bridge strengthening technology. To reinforce the vault economically, efficiently and practically has practical significance.First of all, the author collected many cases of vault damage and analyzed the causes through the arch bridge strengthening cases in recent years. In the principle of structural design optimization, the main arch of non-hinged arch bridge shall be variable cross-section in form. However in order to constructed easily, almost all the non-hinged arch bridge is made to be irrational structure. Although when other cross-section resisting loads, it still has a large surplus capacity. In order to keep lower economy cost, the vault section of the bridge just meets the load. When the load level is greatly increased, the lower edge of the vault section resist tensile stress and the vault area subjected to the maximum positive moment. The damage of vault section is particularly serious.Second, this paper analyzes and summarizes the current situation in arch dome reinforcement. It also describes the characteristics of traditional reinforcement methods (steel bonding, increasing the section method and so on). In addition, it analyzes the shortcomings and the limited circumstances of using traditional methods. Third, the author studied the "influence line load Law" during the process of taking large transport and found the new methods of vault reinforcement. This paper also exhibits three examples of using "impact line loading methods"to reinforce bridges.Last but not least, the reinforcement of Yuancun Bridge is showed as an example of using "impact line loading method" and increasing bridge section. And based on the load test of this bridge, this method is proved to be economic and feasible. |
