Recommendations to assess the shear and punching capacity of one-way slabs under concentrated loads according to the ABNT NBR 6118:2014

Abstract

This study describes a set of recommendations to improve the precision of shear and punching shear capacity predictions for one-way slabs under concentrated loads, regardless of the governing failure mechanism, using the ABNT NBR 6118:2014 code provisions. For this purpose, a database of 143 test results was developed, including one-way slabs with different support conditions and loading layouts and that failed by different shear failure mechanisms: one-way shear, punching shear or a mixed mode. The key parameters influencing the load capacity and failure mechanism of these slabs were considered for the proposed recommendations: load position and slab width. Adjustments to the effective shear width definition and shear resisting control perimeter were described. Arching action for loads close to the support was also considered in both one-way shear and punching shear predictions. Considering the whole database and without separation by the failure mechanism, the ratio between tested and predicted resistances with the one-way shear expressions shows an average value of 1.22 and a coefficient of variation of 18.3%. The respective ratio between tested and predicted resistances with the punching shear expressions reached an average ratio of 1.23 with a coefficient of variation of 21.3%. Therefore, the proposed recommendations allow for reaching enhanced levels of precision in assessing the shear and punching shear capacity of one-way slabs under concentrated loads, regardless of the governing failure mechanism of the slabs.