Distributed Sensing for Shrinkage and Tension Stiffening Measurement

Abstract

A series of reinforcement bar and reinforced concrete specimens were instrumented with fiber optic cables to measure distributed strain profiles along the specimens. The strain due to shrinkage was measured at 3, 7, 21, and 28 days in three specimens to determine the shrinkage strain profile. Reinforcement and reinforced concrete specimens were tested in axial tension and the distributed strain measurements enabled the tension stiffening effect in the reinforced concrete members to be quantified. Due to variations in the development of cracks, measurements on both sides of the reinforcement bar were required to obtain the average strain behavior. The shrinkage strain measurements were also critical in terms of calculating the effect of tension stiffening. The average distributed strain measurements were compared to a proposed tension stiffening model and overall good agreement was seen, although the cracking load was often overestimated by the model.

Crack monitoring in reinforced concrete beams by distributed optical fiber sensors

“…Several factors may have contributed to such discrepancies, the most obvious being the fact that each sensor was attached to a different reinforcement bar of the same beam, causing that cracks propagating in an arbitrary direction which is not completely straight nor perpendicular to the reinforcement might have crossed the rebars at different locations. Other possible reasons for the discrepancies found for beams 3 and 5 could be the removal of a rib in one of the bars to accommodate the foil gauge or even a difference in the relative position of the foil gauge and the DOFS on the rebar, as local bending of the bar has been shown to yield a noticeable variation in the strain measurements (Davis et al, 2017). As a result, an actual difference in strains between the mid-span of each rebar may be expected.…”

“…(Barrias, Rodriguez, et al, 2018;Regier & Hoult, 2015). Consequently, an abundant layer of a one-component water-proof silicone rubber material was applied for protection based on the findings by (Davis et al, 2017). It should be noted that foil gauges and optical fibers were installed in different rebars.…”

“…Henault et al, 2012;Imai et al, 2010) as well as for fibers without any intermediate layer between the fiber and the substrate, frequently attached to the surface of the hardened concrete, see e.g. (Davis, Hoult, Bajaj, & Bentz, 2017;Regier & Hoult, 2015;Rodriguez, Casas, & Villalba, 2015a).…”

Long-Term Concrete Shrinkage Influence on the Performance of Reinforced Concrete Structures

“…Indeed, when dealing with larger structure sizes (skyscraper columns and long-span bridge beams amongst others), shrinkage becomes a predominant structural deformation parameter [ 9 , 10 ]. The observation and monitoring of this phenomenon was recently achieved with Fiber Bragg Grating (FBG) [ 11 ] and the cutting edge monitoring technology represented by distributed optical fiber sensors (DOFS) [ 12 ].…”

Dehnungsmessung bei mehraxialen Druckversuchen an Beton mittels faseroptischer Sensoren

“…Basierend auf dem Coating (Bild 1) variieren die für verlustfreie Weiterleitung des Lichts möglichen Umlenkradien und auch die Steifigkeiten der Fasern [18, 27, 30]. Im Stahlbetonbau eignen sich diese „blanken“ Fasern vor allem für die Applikation auf erhärteten Probekörperoberflächen [31–36] oder entlang von Bewehrungsstäben bzw. innerhalb von in die Stäbe gefrästen oder geätzten Nuten [29, 30, 35, 37–40].…”