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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(a) (c) Fig 3. Load versus CMOD curve for (a) Small, (b) Medium, and (c) Large beams with varying percentages of reinforcement. (b)

The observation is evident in Figure 4 that the large beam's data points cluster close to the LEFM curve when the influence of size is considered, which represents the increasing structural size is correlated with an increase in brittleness. Further, data points corresponding to the medium and small beams lie near the center of the transition between LEFM and strength criteria. Furthermore, it can be observed that for 6 mm, 8 mm, and 10 mm bars in small, medium, and large beams, brittleness number ( β ) has been calculated as 0.641, 0.574, 0.793, 1.282, 1.149, 1.587, 1.923, 1.724 and 2.38 respectively.

Fig. 4. Size effect curve for the present study.

These values fall within the range of 0.1 ≤ β ≤ 10 i.e., the transition zone indicating the exhibition of nonlinear theory of fracture mechanics. To analyze the fracture behaviour of concrete, several fracture properties are needed as input parameters. Fracture energy (G f ), effective crack length (a c ), and fracture toughness (K IC ) are some of these fracture parameters. This section presents fracture parameters obtained from experiments conducted on reinforced concrete specimens of various sizes, including small, medium, and large specimens. 3.1. Fracture properties of reinforced concrete Determining the fracture parameters at various loading stages, such as the peak load, the pre-peak load, and the post-peak load, is necessary for an accurate analysis of concrete in fracture behaviour. From Figure 5(a), It is evident in the small beam, the crack propagation is slower compared to the medium and large beams and after peak load, it propagates slowly. Furthermore, the 10 mm diameter bar requires more load than other diameter bars and has a shorter crack length. From Figure 5(b), the crack propagation in the medium beam is similar to that in the small beam up to the pre-peak load and gradually increases when it reaches the peak load. For the large beam seen in Figure 5(c), the crack propagation increases gradually, and the load abruptly decreases after peak load. From these plots, it is concluded that for large beam sizes, crack propagation becomes easier when it reaches the peak load due to the more rigidness of