Experimental investigation on ultra high-performance concrete beams without shear reinforcement

Abstract

Seven ultra high-performance concrete (UHPC) beams without shear reinforcement are tested in this work to examine their structural behavior as shear failure is a major concern in such members. Coarse aggregate was not used in two of the beams while the other five are made with coarse aggregate as 50% replacement of fine sand. Three longitudinal steel reinforcement ratios (1.14%, 1.64% and 2.46%) and three steel fiber ratios (0, 1% and 2%) are used. Results show that UHPC beams with coarse aggregate show higher ultimate loads (4.7% − 11.5%) than UHPC beams without coarse aggregate and incorporating 1% and 2% steel fiber raises ultimate loads by 60% and 131%, respectively for beams with coarse aggregate. Also, using 2% steel fiber changes failure mode from brittle shear failure by diagonal crack in beams of 0 or 1% steel fiber to ductile flexural failure by yielding of longitudinal reinforcement. Higher stiffness and toughness and lower deflections are observed with the increase of longitudinal reinforcement, steel fiber or coarse aggregate. Using 2% steel fiber highly improved toughness by more than 17 times. Lower rates of improvement are recorded for longitudinal reinforcement and coarse aggregate. However, it is recommended to perform more research to examine more parameters such as fiber types.