Estimation of tension in stay cables at the Indian River Inlet Bridge using frequency based methods
Date
2013
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Publisher
University of Delaware
Abstract
The purpose of this study is to prove that using fiber optic accelerometers in conjunction with dynamic cable theory can be used to measure the tension in eleven cable stays on the Indian River Inlet Bridge. The idea being that the accelerations from the cables vibrations have embedded frequencies that can be extracted using spectral density techniques and processed using MATLAB script files. After the accelerations are processed and the frequencies are extracted and organized, the cables tension can be calculated using dynamic cable theory and cable properties from the bridge design specifications. This study uses two types of vibrations, plucked vibrations and ambient vibrations, to test the sensors abilities to get acceleration time history data that is capable of producing frequency peaks. The results show that the sensors excel in recording accelerations from ambient and plucked vibrations. Also, the results show that the basic dynamic cable equation is a fast and accurate method for calculating cable tensions. It is found that the tensions found in the plucked vibration tests are 0.87 and 0.98 of the final hydraulically measured tensions. This study provides supporting evidence into using in situ accelerometers as a practice for monitoring the long term health of cables on the Indian River Inlet Bridge and other cable stayed bridges.