Conference Agenda

This study describes the implementation of a Cohesive/Overlapping Crack Model (COCM) with the Finite Particle Method (FPM), a meshless numerical analysis technique based on vector mechanics, which is recognized for its efficiency in handling dynamic, nonlinear, and fracture problems. The combined model establishes a robust framework for capturing both tensile and compressive failures in materials such as plain or reinforced concrete. By simulating of three-point bending specimens to prove the model ability to reflect the complex fracture behaviour of concrete structures.

This study predicts the transition between flexural cracking, shear, and flexural crushing failure modes in reinforced concrete (RC) beams through a series of four-point bending simulations on 48 pre-notched specimens. The upcoming experimental setup explores the influence of key parameters, including: (1) longitudinal reinforcement ratios ranging from 0.13% to 2.26%; (2) slenderness ratios (λ) from 3 to 24; (3) beams of varying size-scale with a constant reinforcement ratio; (4) beams of varying size-scale with a constant reinforcement area. The bridged crack model is applied to assess crack propagation and failure mechanisms, providing insight into the mechanical response, ultimate load capacity, and the critical cracks leading to failure. Dimensionless numbers NP and NC are used to capture the brittleness transitions between different failure modes, offering a unified theoretical framework for evaluating these behaviors. The results provide valuable data for understanding the scale effects on brittleness in RC beams.

From the perspective of fractal theory, the bridging effect of the fibres in ultra-high performance concrete (UHPC), may allow only volume cracks, rather than dominant fractures. Experimental tests are carried out to investigate the emitted energy and the fractal domain of the concrete specimens under compression. UHPC and plain concrete specimens with characteristic size equal to 75, 150, and 300 mm, and slenderness 0.5, 1, and 2, are fabricated. All the specimens are monitored using the acoustic emission (AE) sensors. The results indicate that compression strength and ductility of the block specimens exhibit a strong change by varying the sample size. As size and/or slenderness increase, the structural behaviour exhibits a ductile-to-brittle transition, and the final collapse shows a crushing-to-cracking transition. Moreover, the experimental fractal dimension of plain concrete is closer to 2, demonstrating that the fracture tends to occur on a plane (crack surface, 2-D). In contrast, the fractal dimension of fibre-reinforced concrete is close to 3 due to fibre bridging, which avoids the formation of crack surfaces, being the fractal domain very close to a volume (3-D).