Conference Agenda

Steel fiber reinforced concrete (SFRC) is an effective material for structures that must endure dynamic events like impacts, earthquakes, and explosions. Recent studies highlight the role of mechanical properties related to fracture in how concrete responds to blast loads. This study examines high-strength SFRC slabs subjected to such loads. Three self-compacting concrete mixes were developed to explore the effects of varying fiber content on structural performance. Concrete A, with low reinforcement, had 40 kg/m³ of 13-mm long fibers. Concrete B and C added 20 kg/m³ and 40 kg/m³ of 30-mm long fibers to concrete A, respectively. Testing showed distinct softening behaviors among the mixes. After blast tests, concrete B had a higher crack density than concrete A due to greater hardening, while concrete C exhibited superior resistance to crack initiation, resulting in fewer cracks. These results demonstrate that higher fiber content enables better energy dissipation through crack propagation and stress redistribution, enhancing the overall performance of the concrete.

The rising threat of blast and impact events to critical infrastructure has underscored the need for advanced protective solutions to enhance the durability of structural materials. Protective layers can decrease the damage and increase the resistance of structures against such short-term dynamic loading. Different approaches are presented: dispersed fibre reinforcement and endless-fibre textile reinforcement. High-performance concrete with dispersed fibre reinforcement (HPFRC) is recognised for its exceptional strength and resistance to dynamic loading. However, its performance under blast conditions can be further improved with the addition of protective layers. This study investigates how different protective layers and their position affect the damage and structural behaviour of HPFRC subjected to blast loading. One of the protective layers is pliable and made of polyurethane, the other is stiff and made of glass/epoxy. Experiments were conducted using an explosive, placed in direct contact with the panels, to assess damage under different protective configurations. These configurations included uncoated panels, panels with one-sided stiff coatings, two-sided pliable coatings, and panels with stiff layer on one side and pliable layer on the other. On the other hand, textile-reinforced concrete (TRC) with endless carbon fibre reinforcement is used to strengthen existing structures. On the rear side of an impact-subjected structure, the textile-reinforced strengthening layer enables a membrane action and self-centering effect, reduces scabbing, and increases the perforation limit. On the impact-facing side, strengthening layers consisting of a cover layer and a damping layer decrease the impact energy induced into the concrete structure. The findings of all approaches shown in the work demonstrate the potential benefits of adding protective layers, particularly in reducing the scabbing, while also indicating that certain configurations can reduce the likelihood of full perforation. The results also reveal potential disadvantages of applying protective layers, such as increased cracking and reduced residual capacity of concrete structures.

This study examines the tensile fatigue behavior of Ultra-High Performance Concrete (UHPC) reinforced with steel and carbon fibers under cyclic loading. Three specimen types —unreinforced matrix (BM), steel fiber-reinforced (SF), and carbon fiber-reinforced (CF)— were tested using indirect tensile static and fatigue methods with a modified Brazilian test setup. A hinge-based T-shaped loading mechanism ensured stable crack propagation, while strain monitoring combined localized strain gauges with full-field digital image correlation (DIC) for detailed crack behavior analysis. Results indicate tensile strength enhancements of 40% for CF and nearly 3 times for SF over BM. Crack initiation stresses were 7.5MPa (BM), 6.8MPa (CF), and 8.6MPa (SF), with SF specimens demonstrating superior fatigue resistance, sustaining one order of magnitude more cycles than BM. Conversely, CF specimens showed reduced fatigue life due to fiber brittleness and matrix porosity. These findings highlight the influence of fiber type on the fatigue durability and mechanical performance of UHPC under cyclic loading.

Reinforced concrete structures such as offshore supporting structures, bridge decks, road surfaces, machine foundations, etc. are subjected to fatigue loading throughout their service life. Understanding the fatigue behavior of these structures is crucial for ensuring their durability and safety. Fiber-reinforced concrete contains fibrous materials as reinforcement, improving the mechanical properties. Due to the heterogeneity of concrete and variable characteristics of fatigue loading, a multiscale approach is best suited to predict the fatigue life of reinforced concrete. In this study, a linear elastic fracture mechanics (LEFM) based method is attempted to predict the fatigue life of fiber-reinforced concrete using a multiscale approach by modifying the definition of Stress intensity factor (SIF). The nonlinear behavior of the fracture process zone is captured by considering the various toughening mechanisms such as aggregate bridging, fiber bridging and microcracking occuring at meso and micro length scales. The SIF is modified by relating the crack opening displacement at the macroscale and the microscale. This modified SIF based on LEFM approach includes the contributions from bridging stress which occurs due to the bridging of aggregate and fiber at the mesoscale and microcracking occurring at microscale. The modified SIF is validated by computing the fracture energy using available experimental data from literature. Finally, a parametric study is conducted to determine the influence of various parameters on the modified SIF.

Rock-Concrete interface is found in various engineering structures such as dams, tunnels, bridge piers etc. These structures are also subjected to cyclic loading resulting in fatigue. Interface is the weakest and the most critical zone which is susceptible to crack formation and propagation. Understanding the effect of fatigue loading on the rock-concrete interface is useful in predicting the service life of these structures which ultimately ensures the durability of the structure. However, the heterogeneity that lies between rock and concrete poses significant challenge in analyzing the effect of fatigue crack growth at the interface further the fatigue test data exhibit an enormous scatter due to the inherent variability in fatigue strength of material as well as the statistical nature of load experienced by them. Hence, this variation of fatigue life estimation rules out application of any deterministic approach for a reliable prediction of safe life. This paper focuses on proposing a generalized model derived from Paris’ law to predict fatigue crack propagation in the rock-concrete interface. Additionally, it employs a probabilistic approach to estimate the fatigue life of the interface. In order to incorporate the heterogeneity at the interface, effective Young’s modulus (E_eff), is used. The inherent mixed mode condition is included in the Paris’ law through the stress intensity factor in both mode I (K_I) and mode II (K_II). The crack propagation as a function of number of load cycles is predicted under different mixed mode conditions and the same is validated using available experimental results.