Research On The Stress Characteristics Of Asymmetrical Section Box Beam Of Lanxi Jingjiao Bridge

Because of the good performance of structure, Box section is widely used in various bridge structures. Different structure forms of prestressed concrete bridges which with box section is particularly adaptable to the requirement of structure and construction. However, most of box section girder are symmetric section. Symmetric box girder bridge is very mature in the design, construction, management and so on, a variety of theoretical research and technological innovation is very complete. It should be said that it is a very common structure form.With the development of city process, people’demand on the basis of design and construction increasingly, especially for the bridge which across great river as a landmark building.Beside the basic requirements of safe and function, landscape function more and more attention has been paid to the bridge. Therefore, a beautiful, unique bridges are often able to attract people’s attention, and it will become a bright spot in the city. Lanxi Jinjiao bridge can be said to be such a bridge, although it is a prestressed concrete continuous box girder bridge, but due to the asymmetry of box girder and hanging structure and make it do not in general.Asymmetric section box beam and symmetric section box beam, mainly in the following three points difference in the stress characteristics:1. The dead load force does not pass through the shear center, the torque is generated under dead load.2.The web of box girder under dead load and live load force is not uniform;3. The longitudinal prestressing force does not pass through the centroid, the longitudinal prestressing will generate transverse bending moment (moment in the horizontal plane).This paper takes a2*39m cross-section of prestressed concrete box beam of Lanxi Jinjiao Bridge as the research object, discussed and analyzed for the three force characteristics respectively.For the first question, mainly through the optimization of cross-section form, arrangement of each part of the dead load force distribution, try to make the shear centre of the section near the center section, reduce the torque and control it in the allowable range.For the second question, analyse and calculate with solid modeling method. Meanwhile, build a single beam model of box girder, compare the difference between the two kinds of model results in different loading conditions, analyzed quantitatively the degree of uneven force.For the third question, affect the calculated using single beam model can reflect the results of transverse bending moment.Finally, put the degree of uneven force into the single beam model, calculation the bridge fully with considering temperature, settlement and other factors, determine whether the box girder meet the requirements of the occupation standard.