Contribution of concrete and shear reinforcement to the punching shear resistance of column bases

Schmidt, Philipp; Ungermann, Jan; Hegger, Josef

doi:10.1016/j.engstruct.2021.112901

Cited by 13 publications

(9 citation statements)

References 13 publications

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“…Few shear reinforcement elements with large diameters but large spacing to adjacent bars negatively affect the resulting punching load, even if allowable maximum tangential spacing are not exceeded. Previous investigations already indicated the positive impact of finely distributed shear reinforcement elements 7,52,53 . However, systematic test series usable for quantifying the influence of Ø sw,max are not available so that at least more general database evaluations can be conducted to derive application limits and to assess current detailing provisions.…”

Section: Evaluation Of Maximum Punching Shear Reinforcement Diametermentioning

confidence: 99%

“…All in all, the presented database evaluation allows for a more profound definition of Ø sw,max replacing the roughly estimated upper limits of MC2010 or EC2/NAD and paving the way for the novel prEC2 approach, which enables a straightforward determination of Ø sw,max . The stricter limits for larger effective depths accounting for stirrups and single‐leg shear links are also justified as the more progressive design results of prEC2 in case of shear‐reinforced column bases lead to more pronounced steel stresses requiring sufficient anchorage 53 . Future punching test series with systematically varying Ø sw in combination with different tangential spacing and types of shear reinforcement may allow for deriving more progressive upper limits for Ø sw .…”

Section: Evaluation Of Maximum Punching Shear Reinforcement Diametermentioning

confidence: 99%

“…Previous investigations already indicated the positive impact of finely distributed shear reinforcement elements. 7,52,53 However, systematic test series usable for quantifying the influence of Ø sw,max are not available so that at least more general database evaluations can be conducted to derive application limits and to assess current detailing provisions. Of course, stricter detailing rules regarding the allowable tangential spacing could also substitute the limitation of Ø sw,max .…”

Section: Background and Database Compositionmentioning

confidence: 99%

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Critical view on the level of maximum punching strength of flat slabs and column bases using database evaluations

Schmidt

Kalus

Hegger

2021

Structural Concrete

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The level of maximum punching strength is of major importance to design highly stressed slab‐column connections and to choose the type of punching shear reinforcement. Since a couple of years, there is consensus that the maximum punching strength of shear‐reinforced concrete slabs can be defined as a multiple of the reference punching strength without shear reinforcement. The upper bound of this load‐increasing effect depends mainly on the anchorage and arrangement of shear reinforcement elements. Despite numerous research studies and database evaluations, there are ongoing discussions regarding the final effectiveness of stirrups and double headed studs installed in flat slabs and column bases. In this paper, a strictly filtered punching database is used to highlight the significant impact of underlying reference strength comparing the maximum load increase according to current Eurocode 2 and the draft for the next generation of Eurocode 2 (prEC2). Based on this unifying database, the origin of current discrepancies is discussed and a combination of constant lower bound coefficients with a refined formula as specified in prEC2 is proposed. Additionally, the effect of adapting current European Technical Approvals for double‐headed studs and punching shear optimized lattice girders to prEC2 is shortly analyzed. A further database evaluation also allows for setting the basis for optimized detailing provisions regarding the maximum permissible diameter of shear reinforcement.

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Section: Evaluation Of Maximum Punching Shear Reinforcement Diametermentioning

confidence: 99%

Section: Evaluation Of Maximum Punching Shear Reinforcement Diametermentioning

confidence: 99%

Section: Background and Database Compositionmentioning

confidence: 99%

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Critical view on the level of maximum punching strength of flat slabs and column bases using database evaluations

Schmidt

Kalus

Hegger

2021

Structural Concrete

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“…The use of shear reinforcement is also found to affect the punching shear strength of flat slabs, where incorporation of close loop stirrups can significantly increase the shear capacity [17]. Moreover, it was noted that the contribution of concrete to punching shear strength is a function of the amount of shear reinforcement [18]. Similarly, the flexural reinforcement can also increase the punching shear capacity of the slab-column connection for flat slabs with or without shear reinforcement [19].…”

Section: Introductionmentioning

confidence: 99%

Punching Shear Strength Prediction for Reinforced Concrete Flat Slabs without Shear Reinforcement

et al. 2022

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Failure of flat slabs usually occurs by punching shear mode. Current structural codes provide an experience-based design provision for punching shear strength which is often associated with high bias and variance. This paper investigates the effect of adding a horizontal reinforcement mesh at the top of the slab-column connection zone on punching the shear strength of flat slabs. A new equation considering the effect of adding this mesh was proposed to determine the punching shear strength. The proposed equation is based on the Critical Shear Crack Theory combined with the analysis of results extracted from previous experimental and theoretical studies. Moreover, the equation of load-rotation curves for different steel ratios together with the failure criterion curves were evaluated to get the design points. The investigated parameters were the slab thicknesses and dimensions, concrete strengths, size of the supporting column, and steel ratios. The model was validated using a new set of specimens and the results were also compared with the predictions of different international design codes (ACI318, BS8110, AS3600, and Eurocode 2). Statistical analysis provides that the proposed equation can predict the punching shear strength with a level of high accuracy (Mean Square Error =2.5%, Standard Deviation =0.104, Mean=1.0) and over a wide range of reinforcement ratios and compressive strengths of concrete. Most of the predictions were conservative with an underestimation rate of 12%. Doi: 10.28991/CEJ-2022-08-01-013 Full Text: PDF

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“…Urban et al [ 4 ] presented results of an experimental test of thickset reinforced concrete slabs in punching. Schmidt et al [ 5 ] investigated concrete and steel contributions in shear-reinforced column bases with systematically varying shear reinforcement ratios. Sahoo and Singh [ 6 ] experimentally investigated the punching shear behavior of balanced recycled-aggregate concrete-scaled slab–column specimens.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Shear Cap Size and Stiffness on the Distribution of Shear Forces in Flat Slabs

Grabski

Ambroziak

2021

Materials

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The scope of this paper is to investigate analytically and numerically the influence of shear cap size and stiffness on the distribution of shear forces in flat slabs in a slab–column-connections-reinforced concrete structure. The effect of support (shear cap) stiffness on the calculation of the length of the shear control perimeter according to the available methods is presented. Based on the analysis, the authors indicate in what range of support stiffness the corner concentrations become important in the calculation of the punching resistance. For shear caps with high flexibility (α1 ≤ 0.5), the concentration of internal forces in the corners does not occur. The authors compare the numerical results obtained from the calculation methods and indicate the correlations, which can be useful guidance for structural designers. In the case of large shear caps, the simplified MC2010 method gives a significantly lower value of the effective control perimeter length compared to more accurate methods. This paper is intended to provide scientists, civil engineers, and designers with guidelines on which factors influence punching shear load capacity of the slab–column connections with shear caps.

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Contribution of concrete and shear reinforcement to the punching shear resistance of column bases

Cited by 13 publications

References 13 publications

Critical view on the level of maximum punching strength of flat slabs and column bases using database evaluations

Critical view on the level of maximum punching strength of flat slabs and column bases using database evaluations

Punching Shear Strength Prediction for Reinforced Concrete Flat Slabs without Shear Reinforcement

Influence of the Shear Cap Size and Stiffness on the Distribution of Shear Forces in Flat Slabs

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