Crack width, deflection, and strain limits of concrete beams with unstressed seven-wire steel strands as longitudinal reinforcement

ABSTRACT This study designed and tested six prototype beams longitudinally reinforced with either SD420 deformed steel bars, unstressed 1860-MPa seven-wire steel strands, or a combination of these. The experiment revealed that the displacement, crack width, and crack spacing increased with the increasing number of strands used to replace deformed bars as longitudinal reinforcement. Crack width was estimated using Frosch’s equation, which conservatively predicted the maximum crack width for beams with deformed bars and those with both strands and deformed bars; a modified version of the equation yielded more accurate values for the beams reinforced with strands only. A bond coefficient for strands was used in the modified equation. Strain limits for the tension- and compression-controlled sections of the beams with strands were determined to be 0.0145 and 0.0115, respectively. The deflection of the beams was well estimated using the ACI 318–19 equation.