Shear Behavior of Reinforced Concrete Beams with Variable Thickness of Concrete Side Cover

This paper describes a study conducted to investigate the effects of increasing the thickness of the concrete side cover on the behavior of reinforced concrete beams tested in shear. Seven test results are reported. The thickness of the concrete side cover ranged from 5-75 mm (0.2-3 in.) for beams with a target concrete strength of 25 Mpa (3600 psi), and from 25-75 mm (1-3 in.) for beams with a target concrete strength of 40 MPa (5800 psi). The beams were reinforced in the longitudinal and transverse directions. The specimens with 75 mm (3 in.) side cover developed a sharp increase in diagonal crack width upon cracking and showed less favorable behavior. However, at estimated service stresses all specimens either remained uncracked or developed crack widths smaller than a suggested 0.3 mm (0.012 in.) limit. Spalling was observed in the specimens with larger covers near ultimate conditions, but was limited to corners of the section, leaving a considerable part of the cover on the vertical side intact. The ACI shear method and general method provided conservative estimates of the strength.