| The hybrid girder cable-stayed bridge is composed of two kinds of materials, steel and concrete along the longitudinal of the main beam. General, the mainspan of bridge adopts steel beams in order to increase the spanning capacity, while the side-span and part of mainspan adopts concrete beam in order to increase stiffness and add the deadweight. This bridge has been widely used in the field of long-span Bridges due to including the advantages of steel and concrete. The steel-concrete joint section is one of the key structures of the hybrid girder cable-stayed bridge which responsible for the force transmission and deformation coordination between sid-span and mid-span. At present, the hybrid girder cable-stayed bridge the bridge is mainly used in field of highway Bridges, but rarely applied in the railway bridge in our country. Compareing with highway bridge, railway bridge bear bigger live load, so the static and fatigue performance of steel-concrete joint section of highway bridge should get more attention. The mechanical properties of steel-concrete joint section was stuied based on the first hybrid girder bridge——Yong Jiang Bridge in China. The contents of this thesis is as follows.1. The mechanical properties and stress distribution of a single shear stud and PBL shear connector are studied by the FEM of push-out tests. The force transmission characteristics of shear studs and PBL shear connectors of the mixed-model combined the shear studs and PBL shear connectors are investigated when they are arranged in different sections by the nonlinear FEM of the push-out tests.2. A partial full-scale model is designed and manufactured by the FEM of the whole bridge and the principle of equivalent stress, and then both static load and fatigue load are applied to the test model. In static model test, the worst-case of load is applied to the steel-concrete joint section to to investigate the load distribution, load transmission performance of the joint section and stress distribution of the shear connectors. Then, axial force distribution ratio of each component is obtained and analyzed. At the same time, both nonlinear FEM and linear FEM are carried out. The results from nonlinear FEM show that, the friction between and steel beam and concrete beam has little contribution in transmitting shear force. The numerical results calculating from linear FEM show a great agreement with the experiment data. The FEM can well reflect the actual stress state of the model.3. The stress of the joint section is low and the stress of each measure points is stable during the verification fatigue test, which demonstrates the reliability force transmitting and good fatigue performance of structure. The stress of steel beam and shear stud increases obviously due to the separation between steel and concrete, especially on the top position after the destruction fatigue load is applied, but the steel-concrete composite structure still works good and has some fatigue safety reserves.4. Both shear studs and PBL connectors were in charge of transferring shear force in the joint section of Yong Jiang Bridge. The shear studs and the PBL connectors are in linear stress state under the static load. The stress level of the PBL was low, and the stress level of the the front rows shear studs was relatively large, while stress level of the rest is very low. After the fatigue test, the shear studs bearing larger shear were in the plastic stress state and shear force was redistributed during the shear studs. While the stress of the PBL increased but was still in the liner level. The rigidity of the whole shear studs decreased, and a part of shear force transferred by shear studs was distributed to PBL.5. The influences of main structure parameters on the load-transfer mechanism were conducted by FEM, including the thickness of bearing plate, the specifications and distance of shear studs, the thickness of the top and bottom plates and the strength of concrete. The change of force transmission performance of the joint section is analyzed when the first two rows of shear studs which suffers more stress fail.6. The simplified model of the steel-concrete joint section which similar the structure of Yong Jiang Bridge was designed based on the model test and numerical analysis of the joint section and the nonlinear numerical analysis of the shear studs and PBL shear connectors. Then, the stress state of the shear connectors, bearing plate, steel beam and concrete beam are obtained from the nonlinear FEM of the simplified model. At last, the influence on the axial force distribution is researchen which caused by the slip between steel beam and concrete beam... |
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