Title: The Challenge of Predicting the Shear Strength of Very Thick Slabs
Author(s): Michael P. Collins, Evan C. Bentz, Phillip T. Quach, and Giorgio T. Proestos
Publication: Concrete International
Appears on pages(s): 29-37
Keywords: crack, design, load, headed bars
To investigate the shear strength of very thick slabs, a specimen representing a strip cut from a 13 ft (4 m) thick slab was constructed and loaded to failure under an off-center point load. Prior to the test, engineers were invited to provide predictions as to the load magnitude required to cause failure of the specimen, the location where first failure would occur, the load magnitude required to cause failure if both shear spans had contained minimum shear reinforcement, and the load-deformation response for the actual specimen. These predictions, as well as strength predictions based on North American and European design codes were compared with the experimental results. Many of the predictions were found to be very unconservative, including strength predictions based on ACI 318 Code requirements, prompting the authors to recommend using at least the minimum shear reinforcement in very thick slabs.