Study on Retrofitted Masonry Elements under Shear Using Digital Image Correlation

Abstract

Architectural heritage is usually built with masonry structures, which present problems under lateral in-plane loading conditions, such as wind pressure or earthquakes. In order to improve the shear behavior of masonry, the use of a fabric-reinforced cementitious matrix (FRCM) has become an interesting solution because of its synergy of mechanical properties and compatibility with masonry substrates. For a proper structural evaluation, the mechanical behavior of reinforced masonry and the FRCM itself needs to be characterized. Hence, a numerical model to evaluate the FRCM reinforcement requires some mechanical parameters that may be difficult to obtain. In this sense, the shear behavior of masonry can be evaluated by means of diagonal tension tests on small specimens (71 × 71 cm). In this work, a digital image correlation (DIC) monitoring system was used to control displacements and cracking patterns of masonry specimens under shear stress (induced by diagonal tension with FRCM layers) applied to one or two sides. In addition, the mechanical behavior of FRCM coupons under uniaxial tensile tests was also registered with DIC. The displacement measurements obtained by DIC were validated with the measurements registered with LVDT. Unlike LVDT-based techniques, DIC monitoring allowed us to measure deformations in masonry during the full test, detecting crack initiation even before it was visible to the eye.

Textile reinforced mortars (TRM) for repairing and retrofitting masonry walls subjected to in-plane cyclic loads. An experimental approach

“…A total of 12 specimens (six for compression tests and six for shear tests) were built for this purpose. The shear behavior of the masonry specimens was measured through diagonal tension tests in accordance with standard ASTM E519/E519M-15 [39] which has also been used in the experimental research reported in [21]. The size of each masonry sample was 710×710×230 mm (see Fig.…”

“…On the other hand, the opposite side was monitored with a digital image correlation (DIC) system. DIC is a non-contact optical technique used for measuring strain and displacement which has been previously and successfully used in experimental research of masonry structures [21]. The position of each object point in the image can be identified by applying a correlation algorithm using a stochastic intensity pattern (speckle) painted across the specimen's surface.…”

“…A considerable deal of research has been developed to identify TRM's relevant mechanical properties for strengthening masonry or concrete elements. Three relevant areas of research might be identified: mechanical performance of TRM coupons under direct tensile loading [15][16][17][18], testing of TRMstrengthened masonry panels under shear behavior [19][20][21][22], testing of TRM-strengthened masonry arches and vault structures [23,24] and experimental research on out-of-plane TRM retrofitting of masonry walls [25][26][27][28].…”

“…Their effectiveness depends on their application upon one or two sides, as well as the type of mortar and fiber used. In the case of [21], reinforced panels exhibited greater shear strength and ductility, with an amplifying factor around 2.5. Finally, the third area of research focused on masonry arches and vault structures and has shown that TRM composites are capable of restoring the integrity of damaged vault structures and increasing their load-bearing capacity.…”

Testing System for the Mechanical Properties of Small-Scale Specimens Based on 3D Microscopic Digital Image Correlation

“…The digital image correlation method (DIC) has the advantages of being a non-contact approach and having a high accuracy and low environmental and equipment requirements, and has become the most active method in the field of optical measurement. It is widely used for measuring the shape, displacement, and full-field deformation of objects [ 12 , 13 ]. With the help of a stereo light microscope (SLM) vision system, digital image correlation methods can be applied to deformation measurement in small-scale areas [ 14 , 15 , 16 , 17 ].…”