Numerical analysis of high-strength concrete columns interconnected by normal-strength concrete floor

Abstract

The construction methods currently adopted for multi-story concrete buildings resorts the strategy to cast columns and slabs with high and normal compressive concrete strength, respectively. The intersection region affects the load transfer performance of the columns, causing expressive confinement stress in interior columns. However, when the confinement is only provided by two sides, as corner columns, it is not enough to increase the lateral stress. The structural behavior of corner columns, represented by isolated columns, also called sandwich column, is investigated in this paper through numerical nonlinear models. The lateral stresses induced by the uniaxial load applied to the sandwich columns are computed when the influence of concrete strength column-slab ratio, slab thickness and the column width ratio and the biggest dimension of the column's cross section were tested. A set of expressions were proposed to calculate the effective compressive strength of the column based on numerical results. The predicted effective strength has shown a good agreement with experimental results collected from the literature.

Confinement effect of two‐way beam‐and‐slab system on the effective compressive strength of interior concrete columns

“…The influence of concrete strength column‐slab ratio, the steel reinforcement ratio of the column and the beam, beam height and the column width ratio and the largest dimension of the column cross section have been analyzed and the following conclusions can be drawn from the results. The numerical results showed that the parameters with the greatest influence on the stress distribution are the and concrete strengths ratio (). The interior columns confinement results showed a better performance when compared to the sandwich columns, even though the lateral stress was not integral on all four sides. The concrete strength average increase was 13.7% compared to the sandwich columns 22 The effective compressive strength found in columns with a ratio of 5 was equal to , with the exception of the HSC and NSC ratios () of 2.33, 2.67 and 3, which presented increase of approximately 10%. The numerical results for models with a ratio had modest strength gains.…”

“…At point C, confining stresses are expected in direction 1. Still, in direction 3, the confinement will be given in general by the same criterion as that of the sandwich column, 22 even though the beam in direction 3 can have a small influence on this confinement.…”

“…The concrete damage plasticity (CDP) model implemented in the ABAQUS software was used to represent the nonlinear behavior of the concrete and its confinement effect in the interior columns. The certified nonlinear parameters were calibrated by the authors as reported in a previous paper 22 …”

“…The certified nonlinear parameters were calibrated by the authors as reported in a previous paper. 22…”

“…Research studies [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] carried out later sought to investigate other variables intervening in the effective compressive strength of the column (f cef Þ : column width (c), the slab thickness (h), the eccentricity of the load on the column and the beam or slab reinforcement ratio. Of all the authors quoted above, only Azevedo 15 conducted an experimental test considering the column joint presented in Figure 1, that is, a column confined by narrower beams and a thin slab.…”