Numerical and Experimental Investigation of Crack Propagation in Reinforced Concrete Beams Using the Concrete Damage Plasticity Model in Abaqus

Abstract

The structural performance and safety of reinforced concrete (RC) beams are significantly influenced by cracking behaviour under loading. This thesis investigates tensile damage and crack propagation in RC beams using both numerical simulation and experimental validation. The study is rooted in an in-depth literature review covering image correlation techniques for crack monitoring, the fundamentals of structural and non-structural cracks, and the mechanisms of crack initiation and propagation under various load conditions. Based on the insights gained, a comprehensive database of tensile damage behaviour in RC beams has been developed using parametric analysis. The numerical part of the study was carried out using Abaqus software, employing the Concrete Damage Plasticity (CDP) model to simulate tensile cracking under flexural loading. A total of 24 simply supported RC beam models were created, varying key parameters such as the area of tensile reinforcement and the depth-to-breadth (D/B) ratio. Three

categories of tensile reinforcement were examined: under-reinforced, balanced, and over- reinforced doubly reinforced sections. For each category, three D/B ratios (1.2, 1.4, and 1.6)

were analysed with two different beam widths (200 mm and 250 mm), allowing for a broad exploration of structural responses. Each beam was subjected to incremental loading from 10% to 100% of the design load to capture the progression of tensile damage. Across all simulations, tensile cracking initiated in the tension zone below the neutral axis, consistent with theoretical expectations. The under-reinforced sections exhibited the largest crack heights, highlighting their vulnerability to early damage. As the area of tensile reinforcement increased (moving toward balanced and over-reinforced conditions), the extent of tensile damage significantly decreased, demonstrating the beneficial impact of reinforcement on crack control. To validate the numerical findings, experimental tests were conducted using a three-point bending setup on physical RC beam specimens representing the three reinforcement conditions and analytical validation has also been done. The observed crack patterns and damage propagation closely matched the numerical predictions, thereby confirming the effectiveness of the CDP model for simulating RC beam behaviour. A key outcome of this study is the realization that by understanding the relationship between applied load levels, crack propagation, and reinforcement ratios, it becomes possible to predict the residual strength of RC beams. This prediction is crucial for post-damage assessment and for planning effective retrofitting strategies. Engineers can use the developed data to estimate remaining structural capacity and decide whether strengthening, repair, or replacement is needed, thereby improving both safety and resource efficiency in structural rehabilitation. In conclusion, this research not only enhances the understanding of tensile damage in RC beams but also provides a practical tool for damage prediction and retrofit planning, bridging the gap between advanced numerical modelling and field-applicable engineering solutions.