PSI - Issue 66

Ram Lal Riyar et al. / Procedia Structural Integrity 66 (2024) 181–194 Ram Lal Riyar et. al./ Structural Integrity Procedia 00 (2025) 000–000

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infrastructure. It is a substance that performs well in compression but poorly in tension. Steel is inserted as longitudinal bars to withstand the tensile stresses in concrete. The interaction of the concrete and its embedded reinforcement determines the behaviour of reinforced concrete. Reinforced concrete structures are typically designed according to safety and serviceability requirements. When exposed to various loading combinations, the structure should also demonstrate ductile behavior. To satisfy the serviceability requirement, it is essential to accurately anticipate the deflection and fracture of reinforced concrete structures under operating loads. Due to the microstructural interaction and link between concrete and steel, the research on reinforced concrete is significantly more complicated. Concrete structures comprise very small to big structural components with varying reinforcing percentages and are subjected to extreme environmental conditions, including those seen in coastal or industrial areas. Following the theory of the "size effect" in concrete structures, nominal strength, and material brittleness (the energy ratio used during loading before and after the stress-strain peak) constantly decrease with an increase in size of the element given by Bazant (1984). As a result, the concrete components become fully brittle at sufficiently large scales and ductile at sufficiently smaller scales . A zone characterised by intense localized strain and a certain volume, referred to as a "micro-crack region" or "Fracture Process Zone" (FPZ), regularly emerges prior to the formation of distinct macro-cracks. The phenomenon of the deterministic size effect may manifest in reinforced concrete beams that are not reinforced against shear, leading to fractures inside the concrete. At the maximum load, the fractures exhibit comparable courses and relative lengths, irrespective of the beam size. Hence, the size effect phenomenon may be defined using the analytical size effect rule. Since it fluctuates with specimen size, accurate evaluation of the nominal structural strength in laboratory research is challenging due to its sensitivity to FPZ size relative to the specimen size. Weibull (1951) established the first statistical theory, often referred to as the weakest link hypothesis, which states that the structure is only as strong as its weakest element. The structural integrity of a system is compromised when the applied load surpasses the maximum strength capacity of its weakest point when stress redistribution mechanisms are not considered. For constructions with a comparable larger geometry and notches or significant stress-free fractures that increase steadily up to the maximum load, the size effect may be characterised by the analytical size effect law (SEL) given by Bazant and Yu (2005). Bazant and Kazemi (1991) demonstrated that reinforced concrete (RC) beams without stirrups have a size related impact on their shear strength. The authors conducted their experiments using beams that were 1:16 scaled in every dimension (a/D = 3, D = 25-406 mm, and q = 1.65%). A flexure failure was seen in the smallest samples, while a shear failure was observed in the rest. The study conducted by Syroka and Tejhman (2014, 2018) examined the impact of minimal shear reinforcement, supplementary longitudinal bars, and loading conditions. The study demonstrated a stronger correlation between the size effect and its effects associated with crack spacing and crack width rather than the depth of the member. Prasanth et al. (2019) conducted a three-point bending test on beams with notches that were three different sizes and had different strengthening ratios. The beams were put under variable amplitude fatigue loads that increased stepwise over time. Under-reinforced concrete beam failure processes, damage progression, and load-carrying capability are studied by analysis of AE parameters and load-CMOD (crack mouth opening displacement) curve. The reinforcement gives the concrete more sturdiness and strength, enabling it to handle larger loads and fend against damage such as cracking. Reinforced concrete is vulnerable to corrosion when exposed to environmental conditions, such as those prevalent in coastal or industrial locations. The structural integrity of concrete cover is compromised by cracks caused by corrosion, leads to a decrease in the dependability of concrete and ultimately leading to premature collapse of reinforced concrete buildings and infrastructure. Globally, the yearly expenditure on maintenance and repair expenses related to concrete infrastructure impacted by corrosion is projected to be near 100 billion dollars. In real-world situations, corrosion is a slow process that can take months or even years to show any discernible damage. However, in laboratory settings, the corrosion rate can be accelerated to study the impacts of corrosion within shorter time frames. Maaddawy and Soudki (2003) experimentally explored how changing the impressed current density level in the accelerated corrosion process between 100 and 500 µA/cm 2 affected the concrete strain behaviour brought on by expansive corrosion products and the real degree of steel reinforcing bar corrosion. Ye et al. (2018) examined the functionality of corroded RC beams at various intensities of sustained flexural stresses. This study investigated the effects of two distinct accelerated corrosion procedures, namely the galvanic method and the method of artificial environment exposure, on the corrosion properties and reinforced concrete beam performance in a structural context subjected to a load. Hansapinyo et al. (2021) found that a tensile steel bar with pitting or other non-uniform corrosion may break before yielding. Ferrando et al. (2022), in their study of reinforced concrete buildings exposed to marine conditions for over a year, discovered that the calculation of the time required for