Effect of Concrete Strength and Minimum Stirrups on Shear Strength of Large Members

There is concern that current ACI shear design procedures can be unconservative if applied to thick one-way slabs or large beams containing only minimum stirrups. This paper discusses the results of 21 large beams tested to investigate these concerns. Based on the experimental results, the paper concludes that until the current ACI shear provisions are modified, it would be prudent to use the recent shear provisions of the AASHTO LRFD specifications as these provide a more consistent level of safety. A simple spreadsheet is described that enables these provisions to be conveniently applied.