Analysis On Static And Dynamic Properties Of Low- Pylon Cable-stayed Bridge And The Pylon’s Partially Force

Low-pylon cable-stayed bridge is a new species produced during the process of combining basic bridges. It inherits the properties of continuous beam bridge and cable-stayed bridge, and has its own adnantages in the 100 to 300 meters span range.As a typical feature and an important member of low-pylon cable-stayed bridge, stay cable strengthens the main beam by providing vertical fulcrum and axial pressure. The static and dynamic characteristics and seismic response of the main beam under completion state are all influenced by stay cables. Special stress situation may take place when the. cable stays contact with the pylon.Firstly, a three-dimensional basic FEM model is builded in the background of a tower-beam consolidated low-pylon cable-stayed bridge under construction with the application of software Midas Civil.Secondly, referring to the establishment of basic model, the corresponding continuous beam model and models missing part of stay cables are builded. The stress states of all the models under the joint action of weight, prestress and cable force are analysed and compared to study the different contribution of stay cables in above models to the beam’s static performance.Thirdly, multi-Ritz-vector method is applied to analyse the dynamic characteristics of all models established to study the effects of stay cables on natural vibration periods and models of the bridge. Response spectrum method is used according to the bridge site data and aseismic design data to study the responds of models under three dimensional earthquakes and analyse the effects of stay cables during the processes.Fourthly, solid model of the pylon is builded with Midas FEA considering the effects of contact between stay cables and the pylon. Sterss distributions of the pylon, under the joint action of gravity load and cable force, are studied.The weak parts in the members are pointed out.Finally, bar-system and soild FEM models of box girder under maximum cantilever status are estbalished with Midas Civil and Midas FEA, construction stages are set at the same time. Of shear-lag effect, the difference along the box girder under maximum cantilever status and the changes as the construction process is advancing are studied by comparing the results of two models.Contents of this thesis could provide reference for the research and design of similar bridge.