Yangpu Bridge, The Mechanical Characteristic Analysis

The main bridge of Hainan Yangpu Bridge is designed as a hybrid girder cable-stayed bridge with span arrangement (58.5+63+58.5+460+58.5+63+58.5) m, double pylons and two cable planes,which allows two-way six lanes. The side spans are prestressed girders while midspan's joist steel composite-beam structure, which are transited by Steel-concrete combining section. The special structure lead the bridge to complex machenical behavior. The application of the hybrid girder cable-stayed bridge with such main girder cross section form in high way bridges is not common,mechanical characteristics of the bridge and its steel-concrete joint section were researched in this paper, conquered results as follows:1. The spatial finite element model of Yangpu Bridge's full bridge was established by adopting Space Plate-Beam method, analysed the mechanical characteristics under dead load, worst-case of living load, temperature load, wind load, and loads combination. The computation showed that every constructional element of the bridge characterized by reasonable stressing and satisfied the demands of strength and rigidity.2. The mechanical characteristicss of main girder and floor system with or without consideration of confuses soil creep effect were comparatively analysed respectively. The comparation demonstrated that the relative stiffness of floor system reduced with consideration of confuses soil creep effect, the steel main girder beared greater percentage inner force and its innerstress increased while the inner force of floor system decreased.3. Established refined spatial finite element model of the steel-concrete joint section, analysed and studied the mechanical characteristics, which indicated that under every kind of operate condition, all the steel elements and concrete structure were compressed in axial direction of the bridge; The stresses of steel members and concrete were less than design value with large capacity; The stresses in steel and concrete of the steel-concrete joint section were relatively small; The force transmission between Steel-concrete joint section and pure steel segment in the right was relatively smooth, the stress concentrate phenomenon was not fierce in the joint of Steel-concrete combination and pure steel segment or that of steel-concrete combination and concrete segment.4. Researched the mechanical characteristics of the steel-concrete composite section under Overload condition (dead load+1.6 times axial compression under worst-case of living load), which told that the stresses of steel gider were all less than-170MPa in the steel-concrete composite section or the most 1.6m right of the composite section region; The stress of concrete was less than design value-22MPa in the steel-concrete composite section or the most 3m left of the composite section region, which showed that the steel-concrete composite segment had enough bearing capacity.The research has provided analysis for the design of Hainan Yangpu Bridge and has reference value for studying hybrid girder cable-stayed bridges.