Influence of Shear Reinforcement on Thin Web Pretensioned Concrete Beams

Abstract

The objective of this paper is to present the results of the experimental study which was carried out on influence of shear reinforcement of pretensioned concrete thin web beams made with M50 grade concrete. Four pretensioned beams B000, B400, B200 and B100 of the same length, cross section and prestress force were fabricated with no stirrups, 400 mm c/c, 200 mm c/c and 100 mm c/c spacing of stirrups, respectively. The effect of varying percentage of shear reinforcement on cracking load, crack propagation, deflection, ultimate capacity, failure mode and beam ductility was examined. Deflection of the each test beam was measured up to ultimate load at an incremental loading of 2.5 tonne (25 kN). The test results were analyzed for cracking loads and ultimate loads and compared with theoretically estimated values. It has been observed that the loads are found to be increased while increasing percentage of web reinforcement. All the shear reinforced beams exhibited delay in appearance of first crack when compared with beam B000. The reason for the delay in the magnitude of first crack load is recognized as the contribution of shear reinforcement arresting the diagonal shear cracks in the shear zone. The energy abortion capacity of the beams increased while decreasing in the stirrup spacing in the shear span. The beam B100 which was reinforced by double the amount of the web reinforcement than the beam B200 showed a satisfactory margin of safety above 1.50 and ductility response of 3.81.