A comparative evaluation of strain measurement techniques in reinforced concrete structures–A discussion of assembly, application, and accuracy

Abstract

The measurement of strain in structural elements is a necessary means of investigating the condition of a structure, both in research and in practice. The measurement methods for recording strain considered in this work represent both well-established techniques (strain gauges), as well as techniques that are part of rather current research streams (fiber optic sensors, digital image correlation). This work's contribution lies in providing an overarching comparison of these approaches, thereby informing practitioners and researchers as to parameters concerning their assembly, application, and their accuracy. To such ends, two test series were carried out, one on RC tension rods and another on a RC beam in a four-point bending test. From the latter scenario, for example, certain generalizations were to be deduced for varying load levels: low strains are measured well using the fiber optic technique. Conversely, digital image correlation was discovered to be an adequate choice when assessing higher strain levels and concomitant concrete cracking, as this non-contact technique avoids imprecisions caused by adhesives. Findings are to assist the future user by contrasting the three techniques in terms of assembly, handling, application and resilience of sensors, external influences as well as measurement resolution and accuracy. Such practice-oriented remarks should simplify a selection of the suitable measurement techniques catering to the respective, context-dependent testing scenario.

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

“…For reference, a broad spectrum of strain measurement techniques (strain gauges, digital image correlation DIC, FOS, etc.) is available [60]. However, not all methods are equally suited.…”

“…One-dimensional strains along optical fibers are obtained in (sub)millimeter resolution. When appropriately applied (gluing in a groove in the rebar [28,60,61], see Figure 5 center), strains can be acquired along entire reinforcement bars in high resolution. Installation effort and precision depend on the right combination of core, coating and cladding [60].…”

Thermo‐mechanical experiments on reinforced concrete beams: Assessing thermal, mechanical, and mixed impacts on fiber optic measurements

“…The relative displacement of the crack edges (originating from zero in the uncracked state) locally leads to high strains, which are also carried into neighboring parts due to a certain softness of the adhesive of the FOS. Further details can be found in earlier studies 44,45 …”

Stahlfasern ersetzen Bewehrung – Fundamente aus Halbfertigteilen mit hoher Fasermenge

“…Zur Verformungsmessung wurde das optische Messsystem ARAMIS (GOM GmbH) verwendet (Bild 5) [27, 28]. Es nutzt die digitale Bildkorrelation (DIC), die auf dem Vergleich von Oberflächenmustern vor und während verschiedener Belastungszeitpunkte beruht.…”