Size effect on shear resistance of high strength concrete deep beams

Size effect on the shear strength of high strength concrete deep beams was investigated. A total of 12 full-scale reinforced concrete beams without web reinforcement were constructed and tested up to failure. The test variables included the beam depth and the concrete compressive strength. The beams were simply supported and were tested in four point bending. The test results showed that the shear stresses at failure decreased with the increase in beam depth indicating the existence of size effect. Beams of higher concrete strength exhibited more size effect than beams of normal concrete strength. The shear strength of the beams was analyzed using the ACI 318 strut and tie model (STM) provisions, Zhang and Tan’s STM, and kinematic model. The results of the analysis showed that conservative predictions by ACI 318 STM provisions were obtained for the tested deep beams. However, the ACI 318 STM did not capture the size effect. On the other hand, both Zhang and Tan’s STM and kinematic model were found to reflect the effect of beam size in their predictions.