Abstract:
Major factors contributing to the shear behavior in reinforced concrete (RC)
beams have been identified as compressive strength of concrete, shear span to
effective depth ratio, and longitudinal reinforcement. Though significant, few of these
factors are not fully incorporated in ACI code provisions for design of minimum shear
reinforcement. The effect of these factors on shear behavior of RC beams have been
studied analytically by Zararis (Zararis, 2003; Zararis and Papadakis, 2001) but have
not been validated experimentally. To clarify the anomaly and to investigate the effect
of these parameters, an analytical and experimental study was undertaken on the
shear behavior of ordinary strength RC slender beams with moderate longitudinal
reinforcement. Based on this study, modification to Zararis (2003) equations is
proposed on shear behavior of RC beams. The experimental program consisted of
testing of eight simply supported RC slender beams subjected to two concentrated
loads with a shear span of 1016 mm (a/d = 2.5). Test specimens were divided into
four groups based on amount and spacing of minimum shear reinforcement in RC
beams. For comparison and experimental validation of minimum shear reinforcement
in RC beams, specimens were prepared without shear reinforcement, based on ACI
code provisions, Zararis (2003) equations, and modified equations presented in this
study. Ultimate shear strengths obtained in this experimental program are compared
to the analytical shear strengths calculated according to ACI code, Zararis equation
and the modified equation. Test results exhibit that, the proposed equation gives
more accurate prediction of shear capacity of RC beams. Based on the test data, it
was also found that minimum shear reinforcement should be such that it allows
development of nominal flexural capacity in RC beams; accordingly, a new
expression for calculating minimum shear reinforcement is also proposed which
incorporates all contributing factors.
