Application Study On Slab-and-Beam Floor System Used For Strengthening In Double-Arch Bridge

In recent years, with the development of traffic in China, a number of bridges have been damaged to a certain degree. The dangerous bridges are increasing year by year. The carrying capacity of many bridges is falling. In order to insure smooth transportation, it is an urgent affair to maintain or reinforce these bridges. Therefore, to study the strengthening method for the dangerous bridges has deep signification of theory practice in China. Double-arch bridges are the most arch bridges in China in the 1960's and the 1970's, now some different diseases occur in most of them. In this paper, the author studied a kind of slab-and-beam floor system of building which are applied in bridges maintaining and reinforcement while the building above arch was damaged seriously and its main arch is healthy taking the New-yu bridge in Luhe of Nanjing as an example. When maintained, some buildings above main arch ring such as standing pillar or wall, arch circle, side wall would be removed, only reserving main arch ring composed of stomach arch rib, arch wave, arch board and horizontal contact . The arch bending on the top of the original main arch ring corresponds to every arch rib and the bottom beam on its landscape orientation. As a result it becomes a down arc frame similar to slab-and-beam floor system. On the arch bending and bottom beam just established, standing pillar, main beam, horizontal rib beam and bridge front-panel would be built subsequently. Both ends of the main beam would then be put off the new hat beam made of reinforced concrete. Now, it becomes an upper slab-and-beam floor system. Two decks will be joined together on the middle of the bridge, which forms the ability of spanning and loading. With the structure system similar to slab-and-beam floor system, its main beam and main arch circle is united into an Arch and Beam System, completely changing the bearing system of building above it. The bearing capacity exceeds the older arch circle significantly. In the project design, The author made use of a specialized software of Korean MIDAS/Civil to analyse the special structure. The calculation results reveal that the bridge can meet the demand of the design load after maintaining. Advanced new material and new technique were adopted in planting reinforcing steel bar, crack repairing and surface decorations with good results.