Title: CAN DIGITAL IMAGE ANALYSIS PROVIDE AN INSIGHT ON SIZE EFFECT?

Abstract: In quasibrittle materials like concrete, when a crack initiates or propagates the fracture front is blunted by a zone of microcracking that eventually coalesces into an actual crack or an extension of an existing crack. In this zone, which is called fracture process zone (FPZ), nonlinear softening behavior occurs. The research presented in this seminar stems from an experimental study performed to investigate the effect of the size (depth) of the specimen on the fracture response of geometrically similar concrete notched beams. The experimental work is the largest of its kind. Five depths (D), namely 75 mm, 150 mm, 250 mm, 500 mm, and 1000 mm, are considered, while the width (b) is kept constant and equal to 150 mm for all specimens. A new setup is proposed for large specimens. Load responses, peak loads, failure modes, fracture energy, and size effect analysis are presented. The seminar will focus on how digital image correlation (DIC) analysis can be used to identify the fracture process zone and propose a new method to identify the parameters of Hillerborg et al.'s cohesive crack model. The DIC analysis suggests that not only the length of but also the width of the FPZ play a role in the size effect phenomenon. Finally, a simple analytical approach known as cracked hinge model (CHM) is coupled with DIC to investigate the stochastic nature of the fracture process along the ligament.

Bio: CHRISTIAN CARLONI is an Associate Professor in the Department of Civil and Environmental Engineering at Case Western Reserve University. Prior to joining the Case Western, Carloni was an Associate Professor at the University of Bologna (Italy). Carloni is a structural engineer with research interests in fracture mechanics, masonry structures, and composites materials. He has gained extensive experience in experimental mechanics and the use of innovative techniques such as digital image correlation to analyze the fracture process in different applications. He served as ACI/ASCE 446 Committee Chair from 2016 to 2022. Currently, Carloni serves as co-chair of ACI 440k Committee, and is voting member of ACI 549 and ACI 440 Committees, as well as ASTM D30 and ASTM C09 Committees.