Structural Analysis And Disease Prevention Of Prestressed Concrete Curved Girders

With the rapid development of urban rail transit in our country, prestressed concrete curved girder bridges have been used more and more widely. Curved girder bridges are complex space structures, and "bending-torsional coupling" is their most significant mechanical characteristic. Basing on fundamental theory of curved bridges, combined with the finite element method, this paper analyzes the mechanical characteristics of prestressed concrete curved girder bridges in detail and summarizes the influence of radius on their mechanical behavior with the engineering background of Fengsha Bridge in Beijing Metro Line14. With respect to common bridge diseases in the process of construction and operation, the paper also studies the effect of prestress and temperature load on the curved girder. Meanwhile, causes of some bridge diseases, such as side outburst of prestressed tendons, lateral displacement of the main beam, bearing separation and so on are analyzed, and some corresponding preventive measures are provided.The results show that great twisting moment and torsional deflection will be produced under out-of-plane vertical loads, even if the loads are symmetrical. Due to the torque, stress of the two sides of the beam is different, and the support action of the anti-torsion bearing is uneven. With the reduction of curve radius, twisting moment of the curved beam increases, the asymmetry of stress distribution in the main girder is more significant, and the torsional deformation becomes more intense. Therefore, in the design of a curved girder bridge, it is best to choose a larger radius on the premise of meeting other requirements.With a small curve radius or a large pretension, side outburst of prestressed tendons is possible to be caused by radial horizontal distribution of the prestressed force. This kind of bridge disease can be prevented through elaborate design by moving prestressed tendons outward, adding additional anti-collapse reinforcing steel bars, setting diaphragm plate reasonably and checking computation of anti-collapse of the web plate. Prestress and temperature load are the main reasons for the lateral displacement of the main beam and bearing separation. During the design process, sufficient allowable deformation of expansion joints and bearings should be reserved. At the same time, measures should be taken to confine the lateral displacement of the main beam. To avoid bearing separation, space of the anti-torsion bearing could be enlarged to enhance the twisting strength of the curved girder.