The Analysis Of Disease Cause Of Long-span Prestressed Concrete Bridges

With the rapid development of highway in China, the bridge construction has come to a climax period. Long span prestressed concrete constant box girder bridge has acquired wide application at home and abroad in recent 20 or 30 years, it has high stiffness to resist torsion, good integration, it can support positive and negative moments, and has mature and easily applied traits. However, many problems have happened on a large number of already built prestressed concrete constant bridges in construction or usage process, which has seriously affected the normal usage of bridges. Analyzing the disease cause of defective bridges more effectively and deeply, in order to optimize the design and construction of bridges becomes the urgent problem in the engineering field.The study is based on Hanjiang River Bridge in Zhongxiang. According to the design, construction data and experimental record of the bridge, it takes advantage of the curved skew bridge program-WXQ modeling to calculate and use the calculation result to analyze force enduring status of defective bridges, and liner changes during the period of destruction.Meanwhile, the training samples of BP neural network are designed using orthogonal test and the input data of BP neural network consists of concrete strength and pre-stress loss.And the substrution of liner change of each stage of destruction calculated by FEM (WXQ) is made up of the output data. Finally, using network trained, the damage parameters of the structure are then detected by the Genetic Algorithm, and according to data of the concrete stregth and pre-stress loss, the real disease cause of this bridge is estimated.The result of identification indicates the regulation of pre-stress loss. The method not only offers reliable scientific basis for analying the disease cause in the bridge, but also can be popularized and applied to strengthen and optimize designing and constructing those similar to the bridge.