Title: Influence of Slab Openings on the Punching Shear Behavior of Reinforced Concrete Slabs Supported on L-Shaped Columns

Author(s): Graeme J. Milligan and Maria Anna Polak

Publication: Symposium Paper

Volume: 357

Issue:

Appears on pages(s): 187-221

Keywords: punching shear, reinforced concrete slabs, finite element analysis, concrete damaged plasticity model, L columns, irregular slab-column connections, slab openings, unbalanced moment

DOI: 10.14359/51738766

Date: 4/1/2023

Abstract:
Columns supporting reinforced concrete two-way slabs often have non-circular or non-square cross-sections. The punching shear design of alternative column geometries is addressed in ACI 318-19, although the basis for these provisions is unclear as experimental tests of irregular column geometries are limited. In particular, the punching shear behaviour of special-shaped slab-column connections, such as L-shaped connections, has received limited interest. In this paper, nonlinear finite element analysis (FEA) is used to study the influence of column geometry, column location with respect to the slab centroid and the presence of slab openings on the punching shear behaviour of interior L-shaped slab-column connections subjected to gravity loading. The FEA suggests that the diagonal portion of the critical perimeter between the column flanges assumed in ACI 318-19 is ineffective in transferring load between the slab and the column. The FEA also suggests that ideally slab openings around interior L-shaped slab-column connections should be located between the two column flanges of each connection. Locating the openings in this area minimizes their negative impact on punching capacity and is beneficial from an architectural perspective, as the openings and services can be hidden from view. The punching capacities predicted by the FEA, the ACI 318-19 concentric punching shear provisions and the eccentric shear stress model outlined in ACI 421.1R-20 are also compared.