Research On Mechanical Behavior Of U1tra-high Performance Light-weighted Composite Deck In The Urban Cable-stayed Bridge

In the building processes of urban bridges in China,more and more attention has been paid to cable-stayed bridges in the medium-small span bridges.On the basis of reviewing the development history of cable-stayed bridge and the steel deck pavement system,this dissertation has analysed the mechanical behavior of the ultra-high performance light-weighted composite deck structure of the city cable-stayed bridge with the background of the Yiyi bridge in ZhuHai.Firstly,the dissertation has summarized the current status and diseases of steel deck in traditional cable-stayed bridge.Based on the material properties of super toughness concrete,this dissertation has introduced the traditional pavement system and super toughness concrete pavement system.Then,this dissertation has analyzed the whole bridge's property of the urban cable-stayed bridge under the two pavement systems.The results show that the deflection and stress of the main girder under two kinds of pavement system meet the requirements of the code,and the super toughness concrete pavement mainly affects the stiffness of the upper edge of steel box girder.Secondly,the three basic systems of steel bridge deck are expounded.Based on the Yiyi bridge,local finite-element models are built with Ansys software.Then,the local force characteristics of the main girder of cable-stayed bridge under two kinds of pavement system are analyzed.The results show that the lateral effect of the main girder of the single plane cable-stayed bridge with wide bridge deck is very significant.The super toughness concrete pavement mainly reduces the longitudinal stress of the top slab,the transverse tensile stress of the top slab,the longitudinal stress of the U-rib and the transverse stress of the diaphragm.Thirdly,the fatigue theories of steel bridge are introduced and the fatigue finite-element model of steel bridge is established.The dissertation has analysed the fatigue hot spot stress of steel box girder under the two pavement systems.The research finds that the ultra-high performance light-weighted composite deck structure can effectively improve the fatigue of steel box girder.Further analysis of the sensitivity of the fatigue relevant parameters in the the ultra-high performance light-weighted composite deck structure,the results show that choosing a suitable thickness of the pavement to reduce the fatigue stress is more effective than changing the thickness of the top slab,and it is necessary to pay attention to the matching problem between the top slab and the U-rib in the fatigue design of the steel box girder.At last,based on the current joint of the super toughness concrete pavement,a new form of joint,water droplets joint is put forward from the view of the joint configuration.The dissertation has compared the mechanical properties of flush joint,rectangular joint and water droplets joint.The results show that this new joint can improve the stress distribution in the seam area.