Study Of Some Key Technological Problems In Design Of Macau Xiwan Bridge

Macau Xiwan bridge is the first double-layer pre-stressed concrete cable-stayed bridge in the world. For the upper layer, there are six lanes in both directions, and four lanes in the lower layer. To meet the traffic request during typhoon period, a non-inner plate design is applied for the bridge design, and aeration holes are preset in web plates. But the torsion stiffness of box girders will decrease without web plates, and this does not conform to the requests of national and international codes. The holes in web plates would cause stress concentration, which can induce unsafe results.For completing the design of this new bridge structure safely and firmly, this paper analyses the Ao dang 3rd bridge with the help of several kinds of finite element software. Each working condition is studied and the results provide important foundation of the bridge construction and operation. The main achievements are as following:1. Space stress analysis. On the basis of ANSYS, space bar element is applied to simulate the link and pre-stressed steel. Two entity space analyzing models are set up with entity element and plate element. According to the comparison method, the whole structure stress, local girder stress, local hole stress and bridge stress and displacement are analyzes under different working conditions. The computational results provide dependable proof for the whole bridge design.2. Transverse inner force of box girder. Box girder bears large loads for the double layer loads. The author applies the frame analyzing method to analyze transverse inner force of box girder. The computational results provide dependable proof for the bridge section design.3. Stability analysis. Stability analysis is an important part of cable stayed bridge design. Whole and local FEM models are formulated to analyze the structure stability during the construction and operation period, six different work conditions and the cross area of the tower and girder. The stability influence of whole buckling modes, local box girder buckling mode and the cross area of the tower and girder are analyzed under the expected load. The computational results provide technical conference for the bridge stability control design. 4. Earthquake resistance design. On the basis of dynamic analysis, the earthquake motion equation of Xiwan bridge is set up. In order to grasp earthquake response characteristics fully, shell element and space beam element are applied for main girder modeling. The response spectrums of Chinese Highway Engineering earthquake resistance code and earthquake safety estimation report are applied for computation. Through the results comparison, the earthquake resistance design strategy is formulated.5. Wind resistance computation. Through static and dynamic wind computation of Ao dang bridge, the buffeting motion equation is set up. Impulsive wind spectrum is simulated on the basis of ANSYS, and the buffeting effects of the completion stage and the maxim cantilever states are calculated. The Van der put formula and Herzog formula are applied to estimate critical wind velocity of blank tear coupling fluttering and separation torrent torsion fluttering, and dynamic stability analysis of bridge are checked. Meanwhile, the safety analysis of box traveling during typhoon period is tested.For there is no present experience for conference, the design of Xiwan bridge breaks through many requests of national and international codes, and many technical innovation are realized. The first pre-stressed concrete cable reinforced bridge with double layers in the world is set up, which adds a characteristic architecture work to the people. Macau Xiwan bridge has been opened for traffic since Jan 10th, 2005, and the one year operation has verified the reliability of the design strategy and research results. The analyzing program also provides valuable reference for similar projects.