Research On New Structure Of Long Span Suspension Bridge Steel Deck Surfacing

Asphalt surfacing on steel deck of long spanned suspension bridge with steel box girder is a complicated yet still not well solved technical problem. The research and application of deck surfacing in our country of many long spanned steel bridges, especially suspension bridges are disturbed with operational condition of its deck surfacing. Total long spanned steel suspension bridge in our country is up to 10 including those in operations and in constructions. It is not only necessary but also urgent to launch systematic research on deck surfacing of long spanned suspension bridge. Deck surfacing technique for long spanned steel suspension bridge is investigated in the paper, based on technical exploration, theoretical analysis, laboratory tests and trial bridge tests. A new surface system, which consists of gussasphalt at bonding layer and epoxy asphalt at wearing course, is designed to match the requirements of long spanned steel suspension bridge. A trial bridge for this new surface system is constructed to test its suitability followed by a four-year inspection. It can be concluded that the new surface system is suitable for long spanned steel suspension bridge.Firstly, researches on deck surfacing of long spanned steel bridge are reviewed, along with the comparison between deck surfacing and asphalt pavement with sub-base. The mechanical differences between suspension bridge and cable-stayed bridge are compared to get a clear view of the basic requirement for a long spanned steel suspension bridge's deck surfacing.Secondly, static analysis, modal analysis and dynamical analysis under locomotive loads by FEM are employed to analyze static and dynamic responses of orthotropic steel deck pavement system and to give a theoretical support for designing deck surfacing. Steel decks with variable thickness are analyzed with modal methods. Influences of thickness of steel deck on dynamic responses of the whole system is gotten. The results of dynamical analysis reveal that maximum tensile stress in asphalt surface and deflection occurs at mid-span of two adjacent diaphragms, while maximum shear stress at interlayer occurs over diaphragms. In comparison with static and dynamic response of deck surfacing system, it is not safe enough for a designer to use shear stress by static method. It can also be concluded that the mechanical condition of the system with gussasphalt at bonding layer and epoxy asphalt at wearing course is better than that with two layers of epoxy asphalt.Thirdly, epoxy asphalt mixture and gussasphalt mixture are systematically investigated and compared. A new type of epoxy asphalt is specially developed to meet the large flexibility of long spanned steel suspension bridge. Fourthly, new type of deck surfacing system such as gussasphalt at bonding layer and epoxy asphalt at wearing course is designed and tested with other surfacing systems. Properties on extreme temperature, fatigue resistance and so on of every surfacing system are explored and compared. The system with gussasphalt at bonding layer and epoxy asphalt at wearing course plays very well at all tests. By using gussasphalt at bonding layer, maximum tensile strain at the top surface can be greatly decreased, while the compliance of asphalt surfacing to steel deck plate can be increased.Finally, a trial bridge with steel box girder is designed and constructed for a four-year exploration on the operational properties of the new deck surfacing of gussasphalt at bonding layer and epoxy asphalt at wearing course. Strain and deflection of deck surfacing system under real traffic load are measured to validate theoretical analysis results. Paving technology of gussasphalt is also investigated. A four-year inspection of the operational conditions of asphalt surfacing system is launched after the bridge opened to traffic. The surfacing system develops no cracks, ruts, slippage or others distress in the four-year operation, which can be concluded that, the new asphalt surfacing system is suitable for long spanned steel suspension bridge with box girder.