scholarly journals Effect of Shape, Number, and Location of Openings on Punching Shear Capacity of Flat Slabs

Buildings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 484
Author(s):  
Ekkachai Yooprasertchai ◽  
Yonlada Tiawilai ◽  
Theerawee Wittayawanitchai ◽  
Jiranuwat Angsumalee ◽  
Panuwat Joyklad ◽  
...  
Keyword(s):  
Shear Strength ◽  
Standard Deviation ◽  
Experimental Evidence ◽  
Shear Capacity ◽  
Experimental Results ◽  
Punching Shear ◽  
Minimal Impact ◽  
Flat Slabs ◽  
Analytical Results ◽  
Eurocode 2

Experimental evidence have proved that punching shear capacity of flat slabs deteriorate with the presence of openings located within the critical perimeter around columns. It is understood that this deterioration varies inversely with the distance of openings from column’s face. However, effect of the shape of openings on punching shear capacity is not well known. This study presents experimental results of 14 flat specimens to investigate the effects of the number (2 and 4), shape (circular, square, and rectangular), and location (1 and 4 times of slab’s thickness from column’s face) of openings on punching shear strength. It was found that circular openings had least influence on punching capacity followed by square and rectangular openings, respectively. Further, placing openings at a distance of four times the slab’s thickness from column’s face had minimal impact on punching capacity. Further, increasing the number of openings from 2 to 4 substantially reduced the punching capacity. An effort was made to predict the punching capacities of all specimens using the descriptive equations of ACI 318-19 and Eurocode 2. Mean of the ratio of experimental to analytical results and standard deviation of ACI equations were found to be more accurate than those of Eurocode 2 predictions.

scholarly journals Theoretical prediction of punching shear capacity of flat slabs without shear reinforcement strengthened by concrete topping

2021 ◽  
Vol 1203 (2) ◽  
pp. 022108
Author(s):  
Daniel Čereš ◽  
Katarína Gajdošová
Keyword(s):  
Shear Resistance ◽  
Design Guidelines ◽  
Shear Capacity ◽  
Reinforcement Ratio ◽  
Punching Shear ◽  
Shear Reinforcement ◽  
Model Code ◽  
Flat Slabs ◽  
Eurocode 2 ◽  
Model Code 2010

Abstract The main reasons for strengthening flat slabs are the change of the use of a building, increase in the value of loads, degradation of the concrete cover layer, or insufficient reinforcement. This paper is focused on the assessment of punching shear capacity of the strengthened flat slabs without shear reinforcement. One of the possibilities how to enhance punching shear capacity is the addition of reinforced concrete topping. The main goal of this paper is to compare the possibilities for calculation of the increase in the punching shear capacity by investigation of the influence of different thicknesses of concrete toppings and different reinforcement ratio. A reference specimen is represented by a fragment of a flat slab with the thickness of h = 200 mm supported by circular column with the diameter of 250 mm. Three different thicknesses (50 mm, 100 mm, 150 mm) of concrete toppings were considered together with three different reinforcement ratios for each thickness of concrete overlay. Theoretical predictions of the punching shear resistance of flat slabs were evaluated by design guidelines according to the relevant standards: Eurocode 2 (EN 1992-1-1), Model Code 2010 and draft of the second generation of Eurocode 2 (prEN 1992-1-1). The differences in the influence of reinforcement ratio are significant. In Model Code 2010 the reinforcement ratio in concrete topping was considered in equation of moment of resistance. This is unlike in both of the mentioned Eurocodes, where the reinforcement ratio was assumed as a geometric average value of the original reinforcement ratio in the slab before strengthening and of the reinforcement ratio of concrete topping. All the predicted theoretical calculations are based on the perfect connection and bond between the original and new layer of concrete. These predictions should be verified by experimental investigation, which is going to be prepared shortly. By the additional increase in the thickness of concrete topping or in the amount of added reinforcement the attention should be payed to the limitation of the punching shear resistance by the value of the maximum punching shear resistance in the compression concrete strut.

scholarly journals Punching shear resistance of reinforced concrete footings: evaluation of design codes

2018 ◽  
Vol 11 (2) ◽  
pp. 432-454
Author(s):  
D. F. A. SANTOS ◽  
A. F. LIMA NETO ◽  
M. P. FERREIRA
Keyword(s):  
Reinforced Concrete ◽  
Progressive Collapse ◽  
Shear Resistance ◽  
Test System ◽  
Shear Capacity ◽  
Experimental Results ◽  
Punching Shear ◽  
Complex Method ◽  
Shear Design ◽  
Eurocode 2

Abstract Punching is a possible failure mode for slender footings and it may lead a structure to ruin through progressive collapse. Although footing present different geometric characteristics, their punching shear design is based on the empirical methods used for flat slabs. This paper uses experimental results from 216 tests to evaluate the performance of design code recommendations presented by ACI 318 (2014), ABNT NBR 6118 (2014) and Eurocode 2 (2010) to estimate the punching shear resistance of reinforced concrete footings. Great dispersion between theoretical and experimental results was observed, being evident that the test system affects the punching shear capacity of footings. The more complex method proposed by Eurocode 2 resulted in a better correlation with experimental results.

scholarly journals Punching shear strength of waffle flat slabs

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ricardo José Carvalho Silva ◽  
Dênio Ramam Carvalho de Oliveira ◽  
Nívea Gabriela Benevides de Albuquerque ◽  
Francisco Eudázio Suriano da Silva Júnior ◽  
Felipe da Silva Leite
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Failure Modes ◽  
Ultimate Load ◽  
Computational Simulation ◽  
Punching Shear ◽  
Engineering Software ◽  
Flat Slabs ◽  
Eurocode 2 ◽  
Solid Area

Abstract This research aimed to compare the ultimate load of 10 waffle flat slabs with different sizes of solid area and spacing between ribs. For this, a non-linear computational simulation of the slabs was carried out until their failure using the engineering software ANSYS. The failure modes and loads were analyzed, and the results showed that the models with less solid area presented less bearing capacity in comparison to the models with greater solid area when the failure mode was shearing of the ribs. The slabs with the largest solid regions experienced punching shear and behaved in a similar way as solid flat slabs, indicating compliance with the codes in relation to their punching shear strength provisions, especially with the NBR 6118. The results show that a square solid area whose length is 15% of the span is reasonable and that the ACI, Eurocode 2 and NBR 6118 provisions underestimate the shear strength of the ribs.

scholarly journals Evaluation of punching shear capacity of two-way RC slabs without transverse reinforcement according to different provisions

2021 ◽  
Vol 15 (3) ◽  
pp. 171-184
Author(s):  
Tran Xuan Vinh ◽  
Nguyen Trung Hieu ◽  
Pham Xuan Dat ◽  
Nguyen Manh Hung
Keyword(s):  
Failure Modes ◽  
Shear Failure ◽  
Shear Capacity ◽  
Punching Shear ◽  
Test Results ◽  
Flat Slabs ◽  
Comparison Results ◽  
Eurocode 2 ◽  
Effective Depth ◽  
Rc Slabs

Currently, RC flat slabs are being used commonly because of their advantages. Punching shear failure is one of the governing failure modes of RC flat slabs without column capital and drop panels. In this paper, the provisions for predicting the punching shear capacity of two-way reinforced concrete (RC) flat slabs without shear reinforcement including ACI 318-19, Eurocode 2 and TCVN 5574:2018 provisions are reviewed by mean of considering the influences of the main parameters (effective depth, compressive strength of concrete, loaded area, reinforcement ratio). A total of 169 test results collected from the literature were used to compare with the provisions. The aim of this study was to evaluate the level of applicability of predicting the punching shear capacity of two-way RC flat slabs according to these provisions. The comparison results indicated that the Eurocode 2 provision provides the most accurate prediction of punching shear capacity of two-way RC flat slabs.

scholarly journals Fiber Reinforced Polymer Laminates for Strengthening of RC Slabs against Punching Shear: A Review

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 685 ◽  
Author(s):  
Osama Ahmed Mohamed ◽  
Manish Kewalramani ◽  
Rania Khattab
Keyword(s):  
Shear Strength ◽  
Shear Capacity ◽  
Fiber Reinforced Polymer ◽  
Punching Shear ◽  
Fiber Reinforced ◽  
Flat Plates ◽  
Flat Slab ◽  
Flat Slabs ◽  
Reinforced Polymer ◽  
Floor Systems

Reinforced concrete flat slabs or flat plates continue to be among the most popular floor systems due to speed of construction and inherent flexibility it offers in relation to locations of partitions. However, flat slab/plate floor systems that are deficient in two-way shear strength are susceptible to brittle failure at a slab–column junction that may propagate and lead to progressive collapse of a larger segment of the structural system. Deficiency in two-way shear strength may be due to design/construction errors, material under-strength, or overload. Fiber reinforced polymer (FRP) composite laminates in the form of sheets and/or strips are used in structurally deficient flat slab systems to enhance the two-way shear capacity, flexural strength, stiffness, and ductility. Glass FRP (GFRP) has been used successfully but carbon FRP (CFRP) sheets/strips/laminates are more commonly used as a practical alternative to other expensive and/or challenging methods such column enlargement. This article reviews the literature on the methodology and effectiveness of utilizing FRP sheets/strips and laminates at the column/slab intersection to enhance punching shear strength of flat slabs.

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

2022 ◽  
Vol 8 (1) ◽  
pp. 167-180
Author(s):  
Hani Qadan ◽  
Amjad A. Yasin ◽  
Ahmad B. Malkawi ◽  
Muhmmad I. M Rjoub
Keyword(s):  
Shear Strength ◽  
Shear Crack ◽  
Punching Shear ◽  
Shear Mode ◽  
Flat Slabs ◽  
Eurocode 2 ◽  
Wide Range ◽  
Analysis Of Results ◽  
Underestimation Rate ◽  
New Equation

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

Moment and shear transfer between columns and concrete slabs

1990 ◽  
Vol 17 (4) ◽  
pp. 621-628
Author(s):  
Amin Ghali ◽  
Adel A. Elgabry
Keyword(s):  
Shear Strength ◽  
Structural Design ◽  
American Concrete Institute ◽  
Punching Shear ◽  
Vertical Shear ◽  
Concrete Slabs ◽  
Finite Element Analyses ◽  
Shear Transfer ◽  
Flat Slabs ◽  
Punching Failure

Gravity and horizontal forces cause the transfer of vertical shear and moments between concrete flat slabs and their supporting columns. These forces can cause punching failure. Design equations for safety against punching given in the Canadian Standards Association and the American Concrete Institute codes are critically reviewed. It is shown that the equations give in some cases incorrect stresses which do not satisfy equilibrium. A modification is suggested which makes the equations applicable to all cases. The paper also discusses the codes' approach of sharing the resistance to transferred moment between resistances by flexure and by eccentricity of shear, using the coefficient γv. Comparisons are made with the result of finite element analyses. It is concluded that the code equations, with the suggested modification, are adequate, provided that appropriate values are used for the coefficient γv. Key words: columns, connections, flat concrete plates, moments, punching shear, reinforced concrete, shear strength, slabs, structural design.

Numerische Untersuchungen zur Durchstanztragfähigkeit von Flachdeckensystemen/Numerical investigations on punching shear capacity of continuous flat slabs

Bauingenieur ◽  
2018 ◽  
Vol 93 (04) ◽  
pp. 141-151
Author(s):  
D. Kueres ◽  
P. Schmidt ◽  
S. Bosbach ◽  
M. Classen ◽  
M. Herbrand ◽  
...  
Keyword(s):  
Shear Capacity ◽  
Punching Shear ◽  
Numerical Investigations ◽  
Flat Slabs ◽  
Finite Elemente

Das Durchstanztragverhalten von Stahlbetonplatten wird seit mehreren Jahrzehnten experimentell erforscht. Aufgrund des hohen Kosten- und Arbeitsaufwandes von Durchstanzversuchen an Flachdeckensystemen wurde der Großteil der vorhandenen Durchstanzversuche an isolierten Flachdeckenausschnitten durchgeführt. Die Geometrie der Versuchskörper wurde dabei mit dem Ziel gewählt, den Stützmomentbereich um die jeweils betrachtete Decke-Stütze-Verbindung zu simulieren. Günstige Einflüsse, die sich in Flachdeckensystemen zum Beispiel aus Momentenumlagerungen oder Druckmembrantragwirkung ergeben, können in diesen Versuchen nicht auftreten. Daher eignen sich die vorhandenen Versuche in erster Linie zur sicheren Abschätzung der Durchstanztragfähigkeit.   Aufbauend auf theoretischen und experimentellen Untersuchungen aus der Literatur, wird in diesem Beitrag die Durchstanztragfähigkeit von Flachdeckensystemen anhand von nicht-linearen Finite-Elemente-Simulationen genauer untersucht. Das verwendete numerische Modell wird zunächst anhand von Durchstanzversuchen validiert. Nachfolgend wird das Modell für weiterführende Parameterstudien verwendet, um die Unterschiede zwischen Flachdeckensystemen und –ausschnitten genauer zu analysieren. Die Ergebnisse der numerischen Untersuchungen werden abschließend dafür genutzt, einen praxistauglichen Ansatz zur Bestimmung der Durchstanztragfähigkeit von Flachdeckensystemen im Bereich von Innenstützen abzuleiten.

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