PSI - Issue 70

Abutu Simon John Smith et al. / Procedia Structural Integrity 70 (2025) 59–66

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increment in the width of both the flexural crack and the diagonal crack until the width reached 0.87mm and 1.4mm respectively for BS/2/2.82 at ultimate load of 273kN; 0.11mm and 1.6mm respectively for BH/2/2.82 at ultimate load of 258kN; 0.4mm and 1.8mm respectively for BS/3/2.82 at ultimate load of 283kN; and 2.28mm and 3.6mm respectively for BS/2/2.08 at ultimate load of 360kN. The results of load-crack width relationship shown in Figures 3(a) and 3(b) also showed that at ultimate load, the increment in the flexural crack width from the load preceding the ultimate load was 172% for BS/2/2.82, 0.001% for BH/2/2.82, 0.07% for BS/3/2.82 and 153% for BS/2/2.08. In the same way, the increment in the diagonal crack width at ultimate load phase from the preceding load was 87% for BS/2/2.82, 300% for BH/2/2.82, 6% for BS/3/2.82 and 24% for BS/2/2.08. Additionally, the flexural crack width reduced by 87% at ultimate load when hooked-end steel fiber was used instead of straight steel fiber; while hooked-end steel fiber caused the diagonal crack width at ultimate load stage to increase by 14%. The use of 3% V f instead of 2% led to 54% decrease in flexural crack width and 29% increase in the diagonal crack width at ultimate load phase; and this may be due to the increased ultimate load capacity of the beam. A lower a /d of the beam (reduction from 2.82 to 2.08) resulted in 162% and 157% increase in flexural crack width and diagonal crack width respectively; and this is because the shear zone area bearing the shear load became smaller, putting higher deformation pressure on the shear zone and leading to wider flexural crack and diagonal crack. 3.2. Number of Cracks Figure 4(a) revealed that BS/2/2.82 (experiment) at failure developed thirteen cracks, twelve of which were within the shear zone and one within the flexural zone. BH/2/2.82 (experiment) as shown in Figure 4(b) has a total of thirteen cracks when it failed, eleven of it occurred at the shear zone and two occurred at the flexural zone. BS/3/2.82 (experiment) failed with the formation of thirteen cracks, eleven were formed within the shear zone and two within the flexural zone (see Figure 4(c). BS/2/2.08 (experiment) at failure as seen in Figure 4(d) contains eighteen cracks, twelve in the shear zone and six in the flexural zone. The failure mode of both the experimental beams and the simulation beams as can be seen in Figures 4(a-d) are in total agreement.

(a) Crack pattern of BS/2/2.82

(b) Crack pattern of BH/2/2.82

(c) Crack pattern of BS/3/2.82

(d) Crack pattern of BS/2/2.08 Fig. 4: Cracks formed in the UHPFRC - CA beams at failure

The analysis of Figure 5 revealed that the use of hooked-end steel fiber increased the beam’s resistance to crack formation within the shear zone but reduced its resistance to crack formation in the flexural zone. The number of cracks formed within the flexural zone of the beam as seen in Figure 5 increased; and those formed within the shear