New Method for High-Speed Railway Bridge Dynamic Deflection Measurement

The measurement of dynamic deflection is an important component of bridge loading experiments for high-speed railway bridges, but it is difficult to do directly for some long high-speed railway bridges. The deflection curve of the bridge in theory can be obtained by integrating the inclination curve of the bridge. This may be a good indirect method for dynamic deflection measurements of high-speed railway bridges if it meets two conditions: first, it must use a high-precision inclinometer to get a high-precision inclination curve of the bridge, and second, it must have a reliable integration method to calculate the deflection curve from the inclination curve. Based on this theory, the authors propose a new indirect dynamic deflection measurement method that uses precision inclinometers and a reliable integration method to measure the dynamic deflection curves of high-speed railway bridges. First, the authors designed a precision inclinometer called the QY inclinometer; second, the authors propose an inclinometer placement optimization method and a reliable integration method; last, two comparison experiments are conducted to prove this method on the Baima River Bridge. Test results indicate that this method can achieve the same accuracy as the method that uses cable-displacement sensors to test deflection and can achieve 0.01-mm accuracy. These experiments also prove indirectly that QY inclinometers have high precision and a response that is rapid enough to produce a dynamic intimation curve of a beam bridge when a train runs across it at high speed; the integration method proposed in this paper is also reliable. Compared with other methods of dynamic deflection measurement, this indirect measurement method is very easy to execute and does not need a static reference point to install inclinometers, and it can measure the static and dynamic deflection of any long- or short-beam bridge.