Full-field displacement measurement and crack mapping on masonry walls using digital image correlation

Abstract

Understanding the load resisting mechanisms and failure modes of masonry walls loaded in their plane is key to validate mechanics-based analysis and simulation algorithms. Proof load tests are performed on specimens that are extensively instrumented with transducers (e.g., LVDTs, potentiometers, strain gauges), which are typically mounted on a specimen at specific locations. The resulting measurements are local and cannot describe in detail the complex response of infill and confined masonry systems, which may combine bricks, mortar joints, reinforced concrete (RC), and the associated interfaces. In addition, crack maps are typically marked by hand based on visual inspection, making it likely to overlook cracks especially when they have a relatively small width or close after unloading. This paper discusses the feasibility of using digital image correlation (DIC) as a non-contact method to measure displacements on large masonry wall specimens and provide faithful crack maps. Feasibility is assessed based on evidence from in-plane reverse-cycle load tests of two full-scale confined masonry walls. The specimens were designed for two different performance levels in terms of in-plane strength and deformability. Deformability was maximized for the case of a wall that was retrofitted using in-plane (horizontal) reinforcement embedded along the bed joints. The DIC measurements were validated vis-à-vis relevant counterparts from linear displacement transducers, including in-plane drift, diagonal deformations, and interface slip between the RC tie columns and the masonry panel. In addition, faithful DIC-based crack maps were obtained where it is easier to recognize cracks compared with hand marked crack maps on the specimens. © The Society for Experimental Mechanics, Inc. 2014.