| With the produce of prestress technology, prestressed concrete bridge has been widely used in practical engineering and there were 75% prestressed bridge structure.in China. However, prestress loss is always a difficult problem that affects the bridge structure. Prestress loss makes the effective prestress is lower than the design thus influence the structure using performance. There is still no effective method to reduce the loss of prestress. The existing calculation and measurement methods cannot evaluate the effective prestress accurately with complex calculation and high cost. It has great significance to find out simple and effective analysis method for prestress loss. The overload of bridge has been always an important factor that caused bridge damage and affect bridge safety. It is necessary to establish effective overload warning method for bridge health operation.Our study was funded by Science and Technology Project of Jilin Bureau "The health monitoring technology research on the anlongquan interchange of 102 national highway". The object of our study is one prestress concrete simply supported box bridge. Long-term observation for the mid-span strain and vertical deflection data has been conducted. The theoretical and experimental research for prestress loss was done based on the long-term measurement data and the calculation method for the prestress loss was put forward. Based on prestress loss, the overload warming research of bridge was proceeded. The detailed researches are as follows:1. According to the mechanical characters of the bridge, the deformation geometry analysis and mechanical analysis have been done considering the long-term effects of the dead weight and prestress. The relationship between mid-span strain,vertical deflection and load was established and calculation method for the prestress loss of cross section was put forward.2. Introduced the FBG technology and its measuring principle Simply. FBG strain sensor, static level gages and FBG demodulator also have been introduced.Sensor precision was demarcated in the laboratory. Also we expound the data collection process, the composition of remote data real-time transmission system and its working principle.3. Based on the practical engineering long-tern measurement data, the prestress loss of the bridge was analyzed with the method established in the paper. And the calculation has been conducted with bridge design specifications of our country and America which verified the feasibility of calculation method put forward in the paper.4. In view of the actual mechanical state of the bridge after the loss of prestress,the bearing capacity of the bridge at the present stage were analyzed with the finite element model. Based on the measured strain, the bridge overload warning method was proposed. |
