PSI - Issue 70

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

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Also, increase in V f from 2% to 3% positioned the main flexural crack at 8% closer to the nearest support; while same increase in V f resulted in the diagonal crack being 32% farther from the nearest support. Furthermore, Figure 6 revealed that decrease in a /d from 2.82 to 2.08 resulted in the flexural crack’s position being 4% and diagonal crack’s position being 55% closer to the nearest support. Therefore, the position of the diagonal crack in a UHPFRC-CA beam is most influenced by V f , and a /d. The results of the distance of both the diagonal crack and flexural crack from the support is very vital for experimental design of UHPFRC-CA beam to be tested under shear or flexural load, as it will give the researcher a clue of the location of the crack that will cause the beam’s failure. Figure 7 showed that hooked-end steel fiber changed the inclination angle of the diagonal crack from 42 o to 53 o (about 26% increase); and also increased the angle of the flexural crack by 6% from 80 o to 85 o . As seen in Figure 7, the inclination angle of the diagonal crack increased by 36% from 42 o to 57 o with increase in V f ; and it also increased by 10% from 80 o to 88 o for the beam’s flexural crack. As further illustrated in Figure 7, reduction in a /d resulted in 7% increase in the inclination angle of the UHPFRC- CA beam’s diagonal crack (i.e. increased from 42 o to 45 o ); while the flexural crack’s angle increased by 13% from 80 o to 90 o . Critical analysis of the beams’ crack angle revealed that lower a /d is favorable to the formation of the perfect diagonal crack (crack with 45 o inclination angle) that causes shear failure as well as the perfect flexural crack (crack with 90 o inclination angle) that causes flexural failure. 3.4. Crack Angle

BS/2/2.82 BH/2/2.82 BS/3/2.82 BS/2/2.08

0 20 40 60 80 100

Crack angle ( o )

Flexural crack

Diagonal crack

Fig. 7. Crack angle of the beams at failure

4. Conclusions This research work compares the behavior of UHPFRC- CA beams’ flexural crack and diagonal crack when tested under shear load using shape of steel fiber, V f and a /d as research variables. The conclusions drawn from this investigation are as follows: • Hooked-end steel fiber and higher V f significantly improve the resistance of UHPFRC-CA beam to flexural crack widening. Change in a /d has the most influence on both UHPFRC- CA beams’ flexural crack width and diagonal crack width. • Hooked-end steel fiber and higher V f in UHPFRC-CA beam help minimize the number of diagonal cracks formed on its failure face but have the reverse effect along with lower a /d on the number of flexural cracks formed at failure. The impact of lower a /d on the number of cracks (by increasing crack number) helps increase the ductility and shear capacity of UHPFRC-CA beams.