Issue 48

S. Bhowmik et alii, Frattura ed Integrità Strutturale, 48 (2019) 419-428; DOI: 10.3221/IGF-ESIS.48.40 419 Focussed on “Crack Paths” Investigation on fracture process of concrete Sonali Bhowmik, Sandeep Dubey, Sonalisa Ray Department of Civil Engineering, Indian Institute of Technology Roorkee, India-247667 sonarfce@iitr.ac.in A BSTRACT . A series of geometrically similar concrete beams of small, medium and large beam sizes has been tested under the action of monotonic and fatigue loading. Digital image correlation technique has been utilized to understand the fracture processes and crack growth behavior in concrete. The tip of effective crack in concrete beams under static and fatigue loading has been calculated through DIC analysis. Further, existence of size effect has been observed when the results of geometrically similar concrete beams were compared. K EYWORDS . Digital image correlation technique; 2D DIC; Critical energy dissipation; Size effect; Fatigue. Citation: Bhowmik, S., Dubey, S., Ray, S., Investigation on fracture process of concrete , Frattura ed Integrità Strutturale, 49 (2019) 419-428. Received: 01.12.2018 Accepted: 11.02.2019 Published: 01.04.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION ost of the civil engineering structures are subjected to repetitive loading during their service life. Under the application of load, the pre-existing randomly oriented internal cracks/defects slowly localise to form a major cracks which propagate in stable manner up to peak load. Beyond peak, the crack propagation becomes unstable leading to a softening type of behaviour. A considerable size of inelastic zone ahead of crack tip called fracture process zone (FPZ) is responsible for the exhibition of size effect in concrete like material. In heterogenous material like concrete, understanding and modelling of FPZ is complex and challenging. A precise understanding of the formation and behaviour of fracture process zone is very much important and has been attempted in the present study. Fracture energy is an important parameter and governs the fracture behavior. Calculation of fracture energy is generally done by using experimental results of monotonic loading. However, under fatigue loading determination of fatigue fracture energy is important and is lacking in the literature. The fatigue fracture energy is also defined as critical energy dissipation and is associated with the growth of macro-crack in each load cycle, which is equal to the sum of energy dissipations in all nano- scale cracks inside the fracture process zone [1]. Therefore, a thorough investigation on fracture process zone in concrete under the action of fatigue is essential for accurate estimation of critical fracture energy. Attempts have been made by various researchers to characterize FPZ in concrete by following experimental and analytical approaches. Acoustic emission (AE) technique and digital image correlation (DIC) techniques are being commonly used [2-14] now a days through which a better understanding can be achieved on the fracture process ahead of the crack tip. Different phases of fracture process zone has been studied by Mihashi et al. [2] using three-dimensional acoustic emission technique. According to the Authors, fracture process zone is developed at the peak load with an increased absorbed energy. An extension in critical crack width has been observed with the increase in width of fracture process zone. Zhang and Wu [3] have calculated the length of fracture process zone of notched concrete beams under three-point bending test through the M