Study on establishing and testing for strain transfer model of distributed optical fiber sensor in concrete structures

Abstract

When using distributed optical fibers for structural health monitoring, in order to ensure the survival rate of the optical fibers, it is usually necessary to insert the optical fibers into the structure for protection. The coupling performance between the optical fibers and the structure determines the accuracy of the monitoring results. In order to explore the strain transfer law of optical fibers in structures, a strain transfer model based on shear lag theory was established. From analyzing the strain transfer mechanism of optical fibers in structures, the expression of strain transfer efficiency of optical fibers was deduced and the accuracy of the deduced results was verified by comparing with the numerical results. Based on BOFDA technology, two groups of loading tests were carried out to test the strain transfer effect of distributed optical fibers embedded in the test beam. The results have shown that the two ends of the structure were low-efficiency strain transfer zones of optical fibers, which could not fully transfer the strain of the test beam. The middle part of the structure was high-efficiency strain transfer zone of optical fibers, which could completely transfer the strain of the structure. The experimental results were basically consistent with the theoretical deduction. The above research can provide reference for the application of distributed optical fiber technology in engineering structure monitoring.