Comparative Analyses of the Diagonal and Flexural Cracks of UHPFRC-CA beam subjected to shear loading

This study comparatively evaluates the behavior of the flexural crack and diagonal crack of ultra-high performance fiber reinforced concrete beam containing coarse aggregate (UHPFRC-CA) under applied shear load. The beams were tested under four point loading arrangement to investigate the influence that shape of steel fiber, steel fiber volume (Vf) and shear span-depth ratio (a/d) have on their crack behavior. The results obtained from the study showed that decrease in a/d significantly increases UHPFRC-CA beam’s flexural and diagonal crack widths. Hooked-end steel fiber and higher Vf at failure improve UHPFRC-CA beam’s resistance to flexural crack widening. Hooked-end steel fiber and higher Vf help minimize the number of diagonal cracks formed on the failure face of UHPFRC-CA beam. Results also revealed that lower a/d increases the shear capacity of UHPFRC-CA beams through the formation of higher number of flexural cracks in the beams. The use of straight steel fiber and lower a/d in UHPFRC-CA beam provide better assurance for a beam to fail in the mode it is designed to fail due to its crack distance from the nearest support. Lower a/d favours the formation of the perfect diagonal crack (crack inclined at 45o angle) or perfect flexural crack (crack inclined at 90o angle) that causes shear failure or flexural failure. Findings on UHPFRC-CA beam’s crack position from the nearest support can assist researchers to tentatively predict the location of the beam’s flexural crack or diagonal crack during the design stage of an experiment. The findings on the number of cracks formed in the beam can also be used by researchers to better explain UHPFRC-CA beam’s absorption of fracture energy and the improvement of its ductility and shear capacity.