The Detection Of Bridge Dynamic Deflection Based On Tension Wire Displacement Photoelectronic Sensing Technology

The bridge is the one of the most significant infrastructure in highway and railwaysystem. The accident caused by collapse and breakage of bridge occurs repeatedly. Not onlythe economic costs is significant, but also the affection of society is negative. So it is veryimportant to monitor the security of bridge structure and load. The deflection of bridge is amajor index for bridge structure and load, an important component of detection of security,stability and reliability. Now, the existing testing methods are mostly used to measure bridgestatic deflection. Testing methods used to measure bridge dynamic deflection are notperfect,because of environment and coarse precision. A new detection based on tension wiredisplacement photoelectronic sensing technology used for dynamic deflection of bridge waspresented in this paper. Theory research and experimental investigation were done.The tension wire two-dimensional dynamic displacement detection based on lasercollimation beam was developed. The scheme of detecting system was introduced. The lightsource and the selection of tension wire in the system were discussed. The tension wire wasused as reference baseline.CCD was used for receiving optical signals in this system. Thedeflection of bridge could be caught by processing data and analyzing signals. The bridgedynamic deflection measurement in a wide range, the implementation of large-diametercollimated beam, and the calculation method using non-orthogonal light source and CCDwere presented.The detecting calculating method of the edge of photo was described. The edgecalculations methods of threshold value and gradient were recommended, and the feasibilityto extract the edge of photo was introduced. The calculation method to pick up the positionof image point in CCD was discussed. The spliced way of CCD was studied and dataprocessing and fusion was introduced.The detecting system was designed. FPGA was used as logical controller. CCD wasused as signals receiver. DSP was used as signals processer. The signals were send tocomputer through serial port. Software was designed by VC++.A low pass filter wasdesigned to eliminate the influence of fiber shaking. The curve of bridge dynamic deflection could be caught finally.A detection of bridge dynamic deflection was done by using this technology. Theerrors were analyzed. The optical structure and the physical property of tension wire werediscussed.The result have show that the detection based on tension wire displacementphotoelectronic sensing technology for dynamic deflection of bridge is feasible. The bridgedynamic deflection with high precision can be caught at real time in the test of bridgestructure.