This paper designed and fabricated a distributed fiber optic sensing textile for a composite bridge's structural health monitoring (SHM). Based on the Brillouin optical time-domain analyzer (BOTDA), the sensing textile can achieve the resolution of 1m distributed sensing ability. Unlike electrical sensors, fiber sensing systems enjoy the advantages of resistance to electromagnetic interference, survivability withstanding harsh environments, and can interrogation over kilometers. The embroidery machine from Saint-Gobain embedded the fiber system into the textile material. We have designed a U-shape fiber sensing structure including two arms of 22m each. Each arm can be used as a distributed sensing section. Embedded fiber optic sensing textile would result in reduced installation time, which lowers the labor cost and the work stoppage cost, which can be substantial for certain applications like long-range monitoring. Also, textile provides additional protection and allows the design of different layout patterns to accommodate the requirements of a project. The fiber sensing system was installed inside the girder before the bridge was built. We investigated a novel installation method using slides moving inside the girder and epoxy was applied to fix the sensing textile on the bottom side of the girders. The sensing system was tested after the bridge was built and demonstrated the feasibility of distributed fiber sensing system for monitoring composite bridges. The results indicated the potential of distributed fiber sensing systems in structural health monitoring and provide a solution of small size, low cost, high durability fiber sensing system.
Distributed sensors have become a great advantage for Structural Health Monitoring (SHM) as they allow for the multiple points measurement using a single sensor. Nevertheless, the installation of this technology can be time-consuming and have an impact on the overall cost of the project. For this reason, this paper explores the application of different techniques for embedding fiber optic cable into textile for Distributed Optical Sensors which could greatly reduce the installation time. This embedding also provides the ability to design sensors with different patterns that enable monitoring structures like pipelines, bridges, and others. In this paper we have identified an embedding technique that does not damage the fiber optic cable. Additionally, the sensors were tested to study their response to temperature and strain by using Brillouin Optical Time Domain Amplification (BOTDA) interrogation technique.
In recent decades, the use of ultra-high performance concrete (UHPC) has been widely accepted by the construction industry for buildings and bridges. The exceptional properties of UHPC on strength (18 ksi 35 ksi) and durability (freeze-thaw resistance, abrasion resistance, chloride ion penetration resistance) have made it a popular construction material for durable and sustainable civil infrastructure systems. The objective of this paper is to investigate the shortterm mechanical strength development of UHPC specimens using a noncontact synthetic aperture radar (SAR) imaging sensor. UHPC cubes and cylinders were designed and manufactured for nondestructive strength monitoring and kinematic and rheological characterization. Change in moisture content and distribution inside UHPC cylinders was monitored by a laboratory 10-GHz SAR imaging sensor inside a microwave anechoic chamber at UMass Lowell. Hydraulic permeability of UHPC specimens was measured by their bulk electrical resistivity using a concrete resistivity meter (ASTM C1876). The rate of water uptake (absorption or sorptivity) was characterized by an apparatus used to measure the water absorption rate of both the concrete surface and interior concrete (ASTM C1585). Early stage shrinkage behavior of UHPC specimens during the first seven days was also measured using a shrinkage cone. Level of cement hydration in UHPC specimens was quantified by the loss of free water inside UHPC and remotely measured by the SAR imaging sensor. Mechanical strength development in UHPC specimens was monitored by following ASTM C109/C109M. From our preliminary result, it is found that change in SAR amplitude and amplitude distribution can be correlated to the level of strength development.
Differential settlement of underground pipelines is one of the major causes responsible for pipeline failures in the U.S. Due to the invisibility of underground pipeline deformation and the requirement for long-range monitoring of underground pipelines, most of the underground pipeline motions are currently undetected. In this paper, a novel long-range sensing technique using fiber optic sensors is proposed for the structural health monitoring (SHM) the deformation and motion of underground pipelines. Two laboratory 304.8x1.7cm HDPE (high-density polyethylene) pipe specimens were manufactured and tested under four-point bending for damage detection. Single mode optical fibers (10.4 ± 0.8 μm) were installed on the surface of these two HDPE pipes for distributed sensing. Four-point bending test was carried out on two HDPE pipes in the range of 445 N to 2670 N at an increment of 445 N. A BOTDR (Brillouin Optical Time Domain Reflectometer) system was applied in collecting distributed strain measurements (spatial resolution =1m, sampling interval =0.5m) from the two HDPE pipes. Fourteen conventional coil-type strain gauges (gauge factor: 2) were also instrumented on each HDPE pipe for validation purpose. From our laboratory results, it was found that the longitudinal BOTDR strain measurements near the neutral axis of the HDPE pipes can be used for detecting pipe rotation. It was also found that the longitudinal BOTDR strains at the bottom of the pipes can be used to detect pipe bending and damage detection.
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