Distributed strain measurement of a large-scale reinforced concrete beam-column assembly under cyclic loading

In this paper, comparisons are made between the performances of two kinds of distributed sensors, Electric Time Domain Reflectometry (ETDR) cable sensor that is based on the propagation of electromagnetic waves in an electrical cable and Brillouin Optical Time Domain Reflectometry (BOTDR) optical sensor that is based on the propagation of optic pulses and Brillouin scattering that occurs when light is transmitted through the optic fiber. A cable sensor was mounted near the surface of the 80% scale beam-column reinforced concrete assembly that was loaded cyclically until the shear failure occurred. The embedded depth was 0.5 inches. At the same time, a fiber optic sensor was mounted on the surface of the assembly with two installation procedures called Point Fixation (PF) Method and Overall Bonding 5 (OB) Method to measure the strain distribution. Both BOTDR and ETDR sensors were subjected to tension and compression in one loading cycle. Strain distributions obtained from the ETDR and BOTDR sensing systems under different cycle loadings were compared with each other. They were also compared with those measured from the traditional strain gauge.