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【Abstract of the Project】 Continuous bridge is medium span bridges that are commonly used in a bridge structure, prestressed concrete beam is the main structure, prestressed concrete beam has a very wide range of applications. Especially the cantilever construction method, incremental, span construction method in the application of a continuous beam, the full application of the benefits of prestressed technology enables construction machinery, production factory, thus enhancing the construction quality, reduces the cost of construction. Continuous beams of featuring: structural rigidity, deformation is small, dynamic performance, the main beams deflection curve flat, in favor of high-speed driving. It has a joint, rigidity, travelling ride comfort, etc., in 30-120m span is often a bridge-type scheme winners. The transverse prestressed concrete technology in t-beams, box, slab three General span girders, obvious technical economic benefits. To broaden the horizontal tensioning technology, applying it to greater span of continuous beam bridge has become particularly necessary.
Girder is the continuous support in several piers. At load time, the different sections on some positive moment, some have negative moment, the absolute value of the moment were smaller than those in the same span bridge beams. In this way, you can save the main beam of material consumption. Continuous beam typically 3 ~ 5 hole into a United, in a with no deck joints, driving more adapt. Continuous bridge construction, you can set up the main beam-by-hole into a simply supported beam and then connected to a continuous beam. Or from the pier on the stage of a piecemeal overhang the lengthening of the last connection to be the continuous beam. For nearly a decade, the erection of prestressed concrete beams, successfully adopted incremental construction, i.e. in bridge end (or both) on the making of a piecemeal continuous embankment of piecemeal, so that the top to bridge construction is more convenient. Continuous bridge girders of positive and negative moment, structure is more complex. In addition, continuous girder bridge girder is indeterminate structure, substructure of uneven settlement will cause the internal force of the hole. Therefore, continuous beams are generally used for ground conditions, span large bridges. Built in the United States in 1966 kajasto Leah bridge, is currently the largest span steel truss bridge, its span to 376 meter. Prestressed concrete bridge in China's development and application of although only 20 year history, but now in road and City Road and railway construction. At present our country in terms of design, construction, prestressed materials and equipment are made much progress and success, however, and the international level there is a certain gap. Today, we need to continually experience, lessons learned, in design theory, design specifications, materials and construction techniques of the prestressed on evolving and growing, to be creative. Believe that through our concerted efforts, in the 21st century will be our prestressed concrete bridge design and construction standards to update the height.
The content of this design is the bridge design of kunshan highway project.There are four bridge types which to be selected in the design process.They are prestressed concrete Continuous bridge, tied arch bridge ，T-frame bridge and Simple beam bridge. Prestressed concrete Continuous bridge is chosen to be the best one.
The bridge is designed by Ⅲ fairways,.It is a variable cross-section continuous girder bridge with 80 m of the main span.For box-section beam, side-middle-of-span ratio (0.5～0.7); With the request of cantilever construction, the side span is 50 m. For the two independent bridge span structure, every single bridge’s section is single-room box beam. For high deformation curve continuous girder bridge, the fulcrum beam high H is 5.0 m, cross-beam high of middle span is 2.0 m. Beam end of curve; from the internal forces distribution and the aesthetic point of view, we choose the second parabolic curve as the curve of the end of the beam. We select 8 cm thick waterproof concrete as pavement layer and 10 cm layer of asphalt concrete wear as deck pavement. 24bored piles with the diameter of 1.2 m is used in Bridge pier foundation. The height of Cap is 2.4. In order to alleviate water impact on the pier cap, the edge of two caps is arc-like.