In recent years, failings of girders due to overturning in continuous girder bridges have repeatedly occurred in China. To investigate the overturning collapse mechanism and also to evaluate the rationality of anti-overturning design method using beam element models that are commonly adopted in practical design, detailed 3D finite solid element models of a typical single-column pier three-span continuous box girder bridge were built and a full-range numerical analysis of the models was conducted. The solid models included the prestressing effect and diaphragms. Both boundary and geometric nonlinearities were taken into consideration. Bearings were modeled considering the actual construction and dimensions of pot rubber bearings, the material characteristics and boundary conditions of rubber pads, and the contact properties between each part of the bearings. The analysis results revealed that the behavior of the bridge approached the nonlinear state at the onset of first bearing disengagement; the rotation (overturning) mechanism of the girder was gradually transitioned from deformable-body rotation to rigid-body rotation; all the end and middle bearings had been disengaged totally or locally at ultimate overturning failure. The analysis results also showed that bearing disengagements would lead to the ineffectiveness of the constraint in the transverse direction, which significantly reduced the overturning ultimate load and structural ductility before the final collapse. Prior to the first bearing disengagement, the vertical reactions calculated from the beam model were in good agreement with those from the solid model, while the transverse reactions were not. The behaviors were inaccurate after bearing disengagement in the beam models in which the movement of the rotation axis and transition of rotation mechanism failed to be realized. Reliable transverse stoppers and tensile anchors at bearing sections were recommended to efficiently improve anti-overturning stability and ductility in practical design.

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<p>The Shanghai Yangtze Bridge, located over open water at the entrance of the Yangtze River, is currently under construction. A cable-stayed bridge solution with the main span of 730m is adopted to meet the navigational demands of the main channel. The bridge comprises the dual-direction 6-lane expressway and 2-lane traffic railways. In fact, the 730m cable-stayed bridge over the main channel is the longest-spanning bridge of its kind for combined highway and railway traffic. The technical standard is studied to ensure the safety of railway and comfortableness of passengers for the combined highway and railway on the same plane. As the symbolic structure at the mouth of the Yangtze River, it also needs to take the aesthetics into consideration greatly. This paper presents the design and technical characteristics of the main channel cable-stayed bridge.</p>

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Design of Dong Hai Bridge (also known as East Ocean Bridge or East Sea Bridge) considers collision of up to 10,000DWT ships in the main navigational channel. Collision protective dolphins are installed at main piers. This paper describes the design concept and corresponding tests on collision protection for the project. Fixed dolphins are at main piers installed in the transverse direction to the bridge alignment and steel pipe piles are used as foundation. Physical ship collision modelling was made by simulation of the dolphin and ship stiffnesses, which determined the design standard for collision force and provided basis for the shape and design of the dolphins. Integration of dolphins and piers was also proposed Dolphins consisting of a steel spatial structure are at main piers installed as protection along the bridge axis. Mathematical modelling and physical model tests were also undertaken in order to identify the influence of dolphins to wave load on piers, and in order to verify the feasibility and give guidance to design of the steel dolphins.