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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12

The process zone length has been shown to rise with an increase in specimen size, but to decrease with an increase in aggregate size, while the FPZ width has been shown to increase with both an increase in specimen size and an increase in aggregate size, as mentioned by Otsuka and Date (2000). Concrete fracture behaviour is affected by specimen size and heterogeneity in a specific manner. Many images have been analysed using DIC before and after the appearance of the first crack. The image for FPZ has been taken where the fracture processs zone is completely developed. The DIC analysis of that image showed a clear U-displacement and strain which justify the formation of fully developed FPZ. Figure 12 shows the data for the U displacement and strain for the specimen without corrosion with a depth of 200 mm. To better comprehend the behaviour close to the tip, it is useful to examine displacements along a horizontal cross-section as horizontal displacement values along a horizontal line Y (mm) above the notch's point. Normal fluctuation of horizontal displacements with respect to distance, as indicated by the reference lines of control reinforced beam, Y =13.6253, 26.2025, 36.68, 52.405, and 78.6075 mm are presented in Figure 12(b).

Table 2: Fracture process zone length for control and corroded beams with different loading points.

FPZ length of control beam (mm)

FPZ length of corroded beam (mm)

Load (KN)

15

98.535

95.025

20

113.805

110.745

25

116.859

115.987

28.8 1

-

118.083

32.8 2

118.386 - 1 peak load for corroded beam. 2 peak load for control beam.

As the distance from the apex of the notch increases, the magnitude of the horizontal displacement jump decreases and eventually approaches a negligible value, resulting in a virtually horizontal trajectory with no discernible jump. This location can be regarded as the tip of the fracture process zone where there is no discontinuity in displacement along the crack line. However, the minor variations observed in the horizontal displacement values could result from experimental error. The variation of horizontal displacements versus distance corresponding to the reference lines of the corroded reinforced beam is shown in Figure 13 (b). The FPZ length for the control bean was observed as 113.805 mm at 20 KN load, whereas 110.745 mm was observed with the same load in a corroded reinforced concrete beam. Different values of FPZ length for control and corroded beam at load point are reported in Table 2. A decrease in the FPZ length of the corroded beam has been recorded at the same load point as compared to the FPZ length of the control beam. This is due to the degradation of concrete and reinforcement under the action of corrosion. Thereby decreasing the strength (peak load) of the corroded beam compared to the control beam. 4. Conclusions The specimens did not have any shear reinforcement and just one longitudinal bar served as reinforcement. The study included under-reinforced concrete beams with 6mm, 8mm and 10mm diameter reinforcement in geometrically similar beams. The percentage reinforcement with a 6mm bar diameter is 0.27%, 0.14%, and 0.095% for small, medium, and large beams, respectively. For 8mm bar diameter, the reinforced percentage is 0.54%, 0.27%, and 0.16%, and for 10 mm bar diameter, the reinforced percentage is 0.81%, 0.40%, and 0.27% in small, medium, and large beams, respectively. To comprehend their behavior, the specimens underwent three-point bending tests measuring the CMOD and the observations are as follows.