Shear strength of FRP reinforced deep concrete beams without stirrups: Test database and a critical shear crack-based model

Performance of the existing design provisions on fiber reinforced polymer (FRP) reinforced concrete (RC) – FRP-RC – deep beams without stirrups appear to be less robust than when applied to slender geometries. This, coupled with the need for making physical sense of the shear behavior of FRP-RC elements, motivates the present work to extend the Critical Shear Crack Theory to the former, given that the original theory forms the basis for the Swiss design code and the new draft of the Eurocode for shear and punching shear designs. Attributes of deep members such as the geometry of the critical shear crack, the critical section location and the arch action are incorporated into the modified model using special functions and parameters obtained via nonlinear regression, resulting in a model justified with more mechanics and less empiricism than most of the existing design equations. A comprehensive database of deep FRP-RC beams without stirrups was compiled and its behavior thoroughly critiqued with respect to various effective shear strength parameters. The database artifacts and their connection to the less satisfactory performance of the codes/guidelines are discussed. Performance of the developed model was successfully validated using both the training data and blind simulation against the database.