Punching Shear of Thick Plates with and without Shear Reinforcement.

Thick concrete plates are currently used for offshore and nuclear containment concrete walls. In this research, five thick concrete slabs with a total thickness of 300 to 400 mm (12 to 16 in.) were tested under concentric punching loading. Four specimens had no shear reinforcement, whereas the remaining one included T-headed shear reinforcement consisting of vertical bars mechanically anchored at the top and bottom by welded anchor plates. The main focus of this research was to investigate the influence of the size effect on the punching shear strength of thick high-strength concrete plates. All tests without shear reinforcement exhibited brittle shear failures. The addition of T-headed shear reinforcement with a shear reinforcement ratio of approximately 0.68% by volume changed the failure mode to ductile flexural failure. The test results revealed that increasing the total thickness from 350 to 400 mm (14 to 16 in.) resulted in increased punching capacity and at the same time resulted in a small increase in ductility characteristics. An equation based on fracture mechanics principles is recommended to account for the size effect factor. The proposed equation is verified using the test results and is compared with the predictions of different design codes. [ABSTRACT FROM AUTHOR]