Punching shear failure in three-pile caps: Influence of the shear span-depth ratio and secondary reinforcement

The punching formulation of Eurocode 2 allows considering the influence of this ratio, but some interpretation is required whether one deals with pile caps, regarding the effective width of the shear enhancement factor and the definition of the basic control perimeter. A proper definition would prevent unsafe or very conservative results. Therefore, some recommendations for the verification of deep pile caps following the Eurocode 2 are presented. The contribution of vertical stirrups as punching reinforcement is also investigated. The proposed approach is applied to the existing experimental database of three- and four-pile caps to check formulation validity, and conservative predictions with low coefficient of variation are reached.