Shear Strength Components in Reinforced Concrete Members

Abstract

The shear strength (V) of reinforced concrete (RC) beams consists of two parts: shear resistance of concrete (Vc) and contribution of the transverse reinforcement (Vs). Previous experimental results can only give the total shear strength V of a beam. Until now, no existing experimental means could measure the two aforementioned contributions separately with reasonable accuracy during the test of RC beams. This paper reports an experimental method that is able to quantify the two parts in conventional shear tests of RC beams. This was achieved by measuring the strains along the full length of each stirrup in the shear span without disturbing the bond. Thus, the variation in Vc and Vs can be recorded during a beam test. Preliminary tests using this method on particular beams show that not all the shear reinforcement intersecting a critical diagonal crack yields at the onset of shear strength. Both Vc and Vs are not at their maximum values when the shear strength is reached in a beam. The value of Vc is not constant under increasing deformation: it first increases and slightly drops after it reaches a peak, followed by a relatively stable plateau until final shear failure. The variation in Vc with respect to member deformation does not match the predictions of existing models.