New fiber optic sensor for monitoring temperatures in concrete structures during fires

Abstract

This paper proposes a new fiber optic sensor based on Regenerated Fiber Bragg Gratings specially designed to be embedded in concrete structures to monitor temperatures during fire events. A practical test was carried out on a 5.8m long beam subjected to the ISO-834 fire curve for 77 minutes under the typical loads borne by beams in conventional structures. Nine optical sensors were installed at the mid-span section of the beam and were submitted directly to flames and high temperature gradients (of the order of 200ºC/min) that make them measure maximum temperatures of 953º C. The temperatures recorded by the new sensors were compared with those obtained from electrical sensors (thermocouples) and a numerical model, with which they showed a good fit, except in those places in which concrete spalling caused distortions in the results and/or failure of the sensors. The paper thus demonstrates the viability of optical technologies in monitoring reinforced concrete during fires and analyzes sensor behavior to point out areas in which additional research is required.

Recent Progress of Fiber-Optic Sensors for the Structural Health Monitoring of Civil Infrastructure

“…Compared with traditional thermocouple or grating optical fiber sensors, the cost is lower and more data are collected in the same area. In the same year, Gorriz B et al [165] designed a regenerative FBG innovative optical fiber sensor. The maximum temperature of concrete detected under fire conditions is 953 • C. The significance of this research is not only to confirm the feasibility of the optical fiber sensor working in the fire but also to provide further possibilities for exploring higher heat resistance concrete materials.…”

“…Compared with traditional thermocouple or grating optical fiber sensors, the cost is lower and more data are collected in the same area. In the same year, Gorriz B et al [ 165 ] designed a regenerative FBG innovative optical fiber sensor. The maximum temperature of concrete detected under fire conditions is 953 °C.…”

Review of Fiber Optical Sensors and Its Importance in Sewer Corrosion Factor Analysis

“…Temperature enhances the formation of H 2 S in a sewer system [148]. A large number of experimental works have been done on the measurement of temperature in harsh conditions [149][150][151][152][153][154]. DTS has been explored for the implementation of fiber optic DTS in harsh and corrosive sewer environments [155][156][157][158].…”

High Temperature Effects during High Energy Laser Strikes on Embedded Fiber Bragg Grating Sensors

“…FBG sensors are highly sensitive to small changes in axial strain, which is useful in many applications including embedded strain sensors in polymer and polymer-based composites [4,5,6], structural health monitoring in infrastructure [7,8] and airframe structures [9], and measuring the weights of moving automobiles [10]. FBG sensors are also responsive to changes in temperature, which makes them useful in applications such as process monitoring during pharmaceutical production [11] and health monitoring of steel structures [12], fires [13], oil pipelines [14], and laser strike detection [15,16]. This paper focuses on the temperature limits and thermal decay of embedded FBG sensors in such an application.…”