Abstract
Digital Image Correlation (DIC) provides measurements without disturbing the specimen, which is a major advantage over contact methods. Additionally, DIC techniques provide full-field maps of response quantities like strains and displacements, unlike traditional methods that are limited to a local investigation. In this work, an experimental application of DIC is presented to investigate a problem of relevant interest in the civil engineering field, namely the interface behavior between externally bonded fabric reinforced cementitious mortar (FRCM) sheets and concrete substrate. This represents a widespread strengthening technique of existing reinforced concrete structures, but its effectiveness is strongly related to the bond behavior between composite fabric and underlying concrete. To investigate this phenomenon, a set of notched concrete beams are realized, reinforced with FRCM sheets on the bottom face, subsequently cured in different environmental conditions (humidity and temperature) and finally tested up to failure under three-point bending. Mechanical tests are carried out vis-à-vis DIC measurements using two distinct cameras simultaneously, one focused on the concrete front face and another focused on the FRCM-concrete interface. This experimental setup makes it possible to interpret the mechanical behavior and failure mode of the specimens not only from a traditional macroscopic viewpoint but also under a local perspective concerning the evolution of the strain distribution at the FRCM-concrete interface obtained by DIC in the pre- and postcracking phase.
Highlights
Digital Image Correlation (DIC) is a noncontact measurement technique that is increasingly used in several engineering fields
The discrepancies are more evident in the first case of laboratory environmental conditions, wherein the mechanical characteristics of concrete might have a more pronounced influence than in other curing conditions in which, instead, the overall behavior might be mainly governed by the interfacial bond properties at the fabric reinforced cementitious mortar (FRCM)-concrete interface
The resistance of the beam entirely relies on the FRCM contribution; the load-deflection curve in Figure 11 can be separated in two branches, namely the initial beam behavior and the interfacial bond behavior
Summary
Digital Image Correlation (DIC) is a noncontact measurement technique that is increasingly used in several engineering fields. DIC techniques provide full-field maps of response quantities like strains and displacements, which represent a more complete set of information than local measurements obtainable by traditional approaches. What is convenient in DIC is the way in which crack initiation and development throughout the specimen dimensions can be analyzed, a goal that cannot be accomplished via conventional (contact-based) measurement approaches, like displacement transducers and strain gauges. This occurs because strain gauges are capable to measure local values only and because in most practical engineering problems the knowledge of the
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