This paper presents test results of six one-tenth-scale micro-concrete waffle slabs subjected to edge punching shear in the presence of moment transfer perpendicular to the slab’s free edge. Although the observed punching failure mechanism of a waffle slab was found to be very similar to that of a flat slab; the shear capacity is reduced relatively because some of the potential failure surface is lost when it extends into the waffle section.

Because the current codes of practice do not consider the punching shear mechanism of waffle slabs, comparisons with test results revealed that ACI 318-14, BS 8110, and Eurocode 2 overestimated the punching capacities of waffle slabs. An upper-bound plasticity theory model was proposed to predict the punching shear failure load, which gave good agreement with the tests. The proposed model assumes the concrete to be rigid perfectly plastic with the modified Mohr-Coulomb as failure criterion.

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