Large strain-tolerated smart steel strand with built in coaxial cable Fabry-Perot interferometer

A steel strand is the principal force-bearing structural member, and its stress state must be monitored throughout its entire service process. A previously developed optical fiber sensor-based smart steel strand has accomplished self-sensing but with a limited measuring range, and cannot monitor the strain entirely until the steel strand fails. This study aims to develop a large strain-tolerated coaxial cable Fabry-Perot interferometer (CCFPI) smart steel strand. Firstly, a thin CCFPI sensor was proposed by the clamping method using an SF047-type coaxial cable. The test results show that its measuring range can reach up to 140,000 mu epsilon. Subsequently, a glass fiber reinforced polymer (GFRP)-CCFPI smart bar was developed by packaging the CCFPI sensor in a GFRP. Encouraging results of the tensile test were achieved, indicating that the smart bar provides reliable and accurate strain measurements with a dynamic range of 16,000 mu epsilon. Finally, the CCFPI smart steel strand was further developed by replacing the core wire of the steel strand with the GFRP-CCFPI bar. The experimental results show that the tensile strength and elastic modulus of the smart strand were 86.7% and 89.4% of that of the common steel strand, respectively. Moreover, the smart strand was proved to have a large self-sensing range and its tension or stress can be calculated accurately using the strain measured by itself. (C) 2019 Elsevier Ltd. All rights reserved.