Punching shear provisions for reinforced and presfressed concrete flat slabs

1996 ◽  
Vol 23 (2) ◽  
pp. 502-510 ◽  
Author(s):  
N. J. Gardner
Keyword(s):  
Reinforced Concrete ◽  
Correction Factor ◽  
Prestressed Concrete ◽  
Shear Capacity ◽  
Punching Shear ◽  
Concrete Slabs ◽  
Flat Slabs ◽  
Reinforced Concrete Slabs ◽  
Unbonded Tendons ◽  
Effective Depth

The validity of the CSA A23.3-94 code provisions for punching shear were compared with the punching shear results of 142 reinforced concrete flat slabs, 16 prestressed concrete flat slabs with unbonded tendons, and 17 flat slabs with unbonded prestressed and supplementary bonded reinforcement. The code prediction equations are not capable of direct verification against experimental results without using a correction factor. Using a justifiable correction factor, the CSA A23.3-94 provisions are appropriately conservative for reinforced concrete slabs but the scatter is large. However, it was concluded that the CSA A23.3-94 provisions are not conservative for prestressed concrete flat slabs. An equation is proposed to calculate the punching shear capacity of reinforced concrete and prestressed concrete slabs, which has a smaller coefficient of variation than the punching shear provisions of CSA A23.3-94, for symmetrically loaded interior columns. The critical section of the proposed method is the perimeter of the column, which is easier to justify than an arbitrary critical perimeter half the effective depth of slab from the column. Key words: reinforced concrete, prestressed concrete, flab slabs, punching shear.

scholarly journals Prediction of Punching Shear Capacity of Two-Ways FRP Reinforced Concrete Slabs

2017 ◽  
Vol 5 (2) ◽  
pp. 1-7
Author(s):  
Ilker Kara ◽  
Besian Sinani
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Shear Capacity ◽  
Reinforced Concrete Beams ◽  
Punching Shear ◽  
Concrete Slabs ◽  
Design Standards ◽  
Concrete Members ◽  
Reinforced Concrete Slabs ◽  
Frp Reinforcement

An innovative solution to the corrosion problem is the use of fiber-reinforced polymer (FRP) as an alternative reinforcing material in concrete structures. In addition to the non corrodible nature of FRP materials, they also have a high strength-to-weight ratio that makes them attractive as reinforcement for concrete structures. Extensive research programs have been carried out to investigate the flexural behavior of concrete members reinforced with FRP reinforcement. On the other hand, the shear behavior of concrete members, especially punching shear of two-way slabs, reinforced with FRP bars has not yet been fully explored. The existing provisions for punching of slabs in most international design standards for reinforced concrete are based on tests of steel reinforced slabs. The elastic stiffness and bonding characteristics of FRP reinforcement are sufficiently different from those of steel to affect punching strength. In the present study, the equations of existing design standards for shear capacity of FRP reinforced concrete beams have been evaluated using the large database collected. The experimental punching shear strengths were compared with the available theoretical predictions, including the CSA S806 (CSA 2012), ACI-440.1R-15 (ACI 2015), BS 8110 (BSI 1997), JSCE (1997) a number of models proposed by some researchers in the literature. The existing design methods for FRP reinforced concrete slabs give conservative predictions for the specimens in the database. This paper also presents a simple yet improved model to calculate the punching shear capacity of FRPreinforced concrete slabs. The proposed model provides the accurate results in calculating the punching shear strengths of FRP-reinforced concrete slender slabs.

A REVIEW TO PUNCHING SHEAR CAPACTY OF NORMAL AND HIGH PERFORMANCE FIBER CEMENTIOUSE COMPOSITES

2021 ◽  
Vol 25 (Special) ◽  
pp. 4-115-4-126
Author(s):  
Liwaa Abd Alhussen ◽  
◽  
Layth A. Al-jaberi ◽  
Ra’id F. Abbas ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
Shear Failure ◽  
High Performance Concrete ◽  
Shear Capacity ◽  
Punching Shear ◽  
Concrete Slabs ◽  
Slab Thickness ◽  
Shear Stresses ◽  
Reinforced Concrete Slabs

The reaction of column to flat slabs may cause what is known as “punching shear stresses” when the stress is normally concentrated within the perimeter around the loaded area. In general, the reinforced concrete slabs are not designed for any shear failure due to the sudden nature of this type of failure. Many solutions can be followed to overcome such issue like increasing the depth of slab and diameter of columns. Increasing the slab thickness may add extensive dead loads and can breaks the economy justifications of this structural member. On the other hand, increasing the diameter of any column may un accepted due to architectural purposes. The high performance concrete is such type of concrete that illustrate high levels of mechanical performance “structural behavior as a consequence” if compared with normal concrete. Due to that, the high performance concrete may give good alternative an exceeds the problem of punching as a result. The basic aim of this study is to propose a brief review regarding this field of research. However, this study is divided to three parts, the first is devoted to view a suitable background about the punching shear capacity of traditional concrete slabs. The second part is registered to view the past experience in reinforced concrete slabs punching capacity and have steel fibers while the second part is devoted to present the state of art concerning the punching shear of high performance concrete slabs.

scholarly journals NUMERICAL STUDY OF THE PUNCHING SHEAR MECHANISM FOR THIN AND THICK REINFORCED CONCRETE SLABS

2021 ◽  
Vol 17 (4) ◽  
pp. 91-105
Author(s):  
Oleg Kabantsev ◽  
Sergey Krylov ◽  
Sergey Trofimov
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
Great Influence ◽  
Shear Capacity ◽  
Punching Shear ◽  
Concrete Slabs ◽  
Longitudinal Reinforcement ◽  
Shear Mechanism ◽  
Reinforced Concrete Slabs ◽  
The Difference

The assessment of the punching shear capacity for reinforced concrete slabs, carried out according to the regulatorydocuments of a number of countries, leads to significantly various results. At the same time, the results of thecalculated forecast may have great differences from the experimental data. A great influence on the accuracy of the resultsof the calculated forecast is exerted by the thickness of the examined slabs, as well as the value of longitudinal reinforcement.These parameters determine the features of the mechanisms of destruction of slabs in case of the punching shearmechanism, as indicated by individual interpretations of the results of experimental studies. In order to determine thefeatures of the punching shear mechanism of reinforced concrete slabs of various thicknesses, numerical studies of theprocess of cracking and destruction of slabs of different thicknesses have been performed. Differences in the mechanismof formation and development of cracks in thin and thick slabs are revealed. The paper shows that the behavior of thinand thick slabs has qualitative distinctions at the initial stages of formation and development of the cracks leading todestruction. The authors have also shown the difference between stress-strain state of thick and thin slabs before destruction.In conclusion, it was established that the influence of longitudinal reinforcement on the strength during punching inthick slabs is much less than in thin ones.When evaluating the punching shear capacity of reinforced concrete slabs, the regulatory documents of different countries give significantly different results. In this case, the calculation results may differ significantly from the experimental data. The deterioration of the thickness of the calculated slabs, as well as the value of the longitudinal reinforcement has a great influence on the accuracy of the calculation results. These parameters determine the features of the destruction mechanisms of slabs under punching. This fact is indicated by some interpretations of the results of experimental studies. In order to establish the peculiarities of the punching shear mechanism of reinforced concrete slabs of different thicknesses, a numerical investigation of the cracking and destruction of slabs of different thicknesses have been performed. Differences in the mechanism of formation and development of cracks in thin and thick slabs have been revealed. The paper shows that the behavior of thin and thick slabs has qualitative differences at the initial stages of the cracks formation and development that leads to destruction. The difference between stress-strain state of thick and thin slabs before breaking have been shown. It was found that the effect of longitudinal reinforcement on the punching shear strength in thick slabs is much less than in thin ones.

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