Influence of the column rectangularity index and of the boundary conditions in the punching resistance of slab-column connections

Abstract

Experimental evidence indicates that both the column rectangularity index and the boundary conditions of the connection may affect the ultimate punching resistance. This paper presents general aspects of these topics and, through the analysis of experimental results of tests on 131 slabs, evaluates the accuracy and suitability of recommendations presented by ABNT NBR 6118, Eurocode 2, ACI 318 and fib Model Code 2010. Experimental results showed that the security level of normative estimates trend to reduce as the column rectangularity increases, and in some cases, the punching resistance was overestimated. Finally, adjustments are suggested in equations presented by NBR 6118 and MC2010 in order to eliminate this trend of unsafe results.

Mechanical model for punching shear capacity of rectangular slab‐column connections

“…Their study revealed that, in contrast to Eurocode 2 (EC2), 3 the increase in aspect ratio results in an unsafe estimation made by ACI. The fact that stress distribution along the control perimeter in rectangular columns is not uniform was confirmed by Teng et al, 4 Hawkins et al, 1 Moe, 5 and Urban. 6 Teng et al 4 introduced a factor, β, to take into account the column rectangularity.…”

“…Hawkins et al 1 investigated the influence of column rectangularity on punching strength of slab-column connections. They showed that the shear capacity was consistent with those calculated from ACI for specimens with aspect ratios less than 2 but inconsistent with greater aspect ratios.…”

Experimental investigation of punching shear behavior of flat slabs supported by rectangular columns and loaded with various load patterns

“…Current standards such as EC2 (2004) and ACI 318‐19, prEC2 (2021) and Model Code 2010 do not distinguish these situations in predicting punching shear capacity. Oliveira 7,12 proposed flexural factor λ i ≥ 1.0 for correction punching shear resistance accounting for column rectangularity and flexural behavior of a slab. The factor is applicable to the MC1990 and EC2 (2004) models for predicting punching shear capacity.…”