Field measurement and analysis on the prestress loss of a long-span PC box Girder Bridge

The crack and large deflection of long-span PC box Girder Bridge is common in their service stage. The lower estimation for the loss of prestress is one of possible reasons. Combined with a long-span prestressed concrete box girder bridges, the loss of longitudinal and vertical prestress of a long span PC box girder bridge is measured during the construction and service stage. Based on the measured results, the loss of the longitudinal and vertical prestress of the long-span PC box girder bridge is analyzed by GA-ANN method and the code of JTG D62-2004, respectively. The results demonstrate that the instantaneous loss of the longitudinal prestress is more than 40% of the designed value, and the total loss of the vertical prestress is about 40% more than the designed one as well. The value of the prestress loss is much higher than the expected one of the design. The reason lies in the inappropriate construction technology, such as not tension the prestress to the designed value, tension at an early age, and excessive different of the tube wobble and so on. Therefore, the engineering quality control must be strengthened during the construction stage of the long-span PC box girder bridge for avoiding excessive prestress loss.