Reinforced concrete flat slabs with openings at different distances from the column

Abstract

The increase in the use of flat slabs and the need of the openings for the passage of installations, such as hydraulic and electrical, which significantly reduces the punching shear resistance capacity of the slab, makes the understanding of the influence of openings in this type of structure extremely necessary. The influence in the structural behaviour of flat slabs with openings at different distances from the column was investigated through five square slabs (1,800 mm x 1,800 mm x 130 mm) supported on square columns (150 mm x 150 mm) tested until failure. The results obtained experimentally were compared with results available in the literature, as well as with responses predicted from the normative instructions. The results confirm high stresses concentration in the region between the column and the opening and that opening situated at 3d from the column have no influence on the failure load for the tested slabs.

Enhancement of the punching shear verification of slabs with openings

“…In the last decades, many studies have been performed to investigate punching shear in flat slabs with openings and without shear reinforcement, either numerically or experimentally. [1][2][3][4][5][8][9][10][15][16][17][18][19][20][21][22][23][24][25][26] Test results are now available for a wide variety of column dimensions as well as geometries and locations of the openings. Nevertheless, the current code approaches to account for the strength reduction due to openings, originally validated on the basis of limited experimental results (square columns, square, and circular openings) have not been updated to account for recent results.…”

“…1,20 The database includes a total of 68 slabs without transverse reinforcement. [1][2][3]8,[17][18][19][20][21][22][23] Table 1 shows the reinforcement ratios obtained from fib MC 2010:2013 and EN 1992-1-1:2004, as well as properties of the slabs. Nevertheless, in some cases, fib Model Code 2010 and prEN 1992-1-1:2021 also give overly conservative estimates of the punching shear resistance.…”

“…In the last decades, many studies have been performed to investigate punching shear in flat slabs with openings and without shear reinforcement, either numerically or experimentally 1–5,8–10,15–26 . Test results are now available for a wide variety of column dimensions as well as geometries and locations of the openings.…”

“…The database includes a total of 68 slabs without transverse reinforcement 1–3,8,17–23 . Table 1 shows the reinforcement ratios obtained from fib MC 2010:2013 and EN 1992‐1‐1:2004, as well as properties of the slabs.…”

Nonlinear analysis of the impact of openings on punching shear strength

“…Many researchers in Brazil and abroad have studied the influence of openings close to columns in reinforced concrete flat slabs. [3][4][5][6][7][8][9][10][11][12][13][14] Although the structural system of flat slabs is widely applied in structural projects, the models proposed by the codes and normative prescriptions have limited experimental observations. 8 The current design codes for punching shear account for the effect of openings on the slab's ultimate capacity based on size and location, by reducing the critical/control perimeter.…”