What is a punching shear failure?
Punching shear is a type of failure of reinforced concrete slabs subjected to high localized forces. In flat slab structures, this occurs at column support points. The failure is due to shear. This type of failure is critical because no visible signs are shown prior to failure.
What causes punching shear failure?
General Mechanism of Failure Punching shear is a phenomenon in flat slabs caused by concentrated support reactions inducing a cone shaped perforation starting from the top surface of the slab.
How do you check punching shear in footing?
Punching shear is produced directly by the forces and moments acting on the column. For the simple case of a concentric footing with a downward load, the punching shear can easily be calculated as the volume of the bearing pressures on the critical area around the column.
What are the characteristics of punching shear failure?
The Punching shear in reinforced concrete slabs is treated as a 2D analog of the shear experienced in beams. This type of failure happens because of a unexpected rupture. This rupture becomes uncontrollable with the help of prime reinforcement.
How do you stop a punching shear failure?
To overcome the punching failure problem, there are many ways to increase the punching shear strength of concrete slabs, increasing slab thickness in the area adjacent to the column, increasing column thickness which is against the architectural desire, and finally providing slab with shear reinforcement.
What is punching shear capacity?
Punching shear is a phenomenon where a concentrated force on a slab causes a shear failure cone that “punches” through. Punching shear calculations require a demand value and a capacity value. Many hand calculations will consider a punching shear force against a punching shear capacity force.
What is general local and punching shear failure?
Local Shear Failure – This type of failure occurs in medium dense sand with relative density between 35 – 70 %. In this type of failure, failure takes place at a very large strain. Punching Shear Failure – This type of failure occurs in loose sand or soft clay with relative density less than 35 %.
How can I increase my punching shear resistance?
What is punching shear in RCC footing?
The punching shear is a failure mechanism in structural members like slabs and foundation by shear under the action of concentrated loads. The action of concentrated loads is on a smaller area in the structural members. In most cases, this reaction is the one from the column acting against the slab.
How do you overcome shear failure?
Since shear failure is frequently sudden with little or no advanced warning, the design for shear must ensure that the shear strength for every member in the structure exceeds the flexural strength. Providing proper shear reinforcement along the beam will reduce the possibilty of shear failure along the beam.
What is maximum stress theory?
“The maximum shear stress theory states that the failure or yielding of a ductile material will occur when the maximum shear stress of the material equals or exceeds the shear stress value at yield point in the uniaxial tensile test.”
What is punching shear failure and how to prevent?
Punching shear is a phenomenon in flat slabs caused by concentrated support reactions inducing a cone-shaped perforation starting from the top surface of the slab. Although generally preceded by flexural failure, punching shear is a brittle failure mode and the risk of progressive collapse requires a higher safety class in structural design.
What does punching shear mean in concrete slabs?
Punching shear is a type of failure of reinforced concrete slabs subjected to high localized forces. In flat slab structures this occurs at column support points. The failure is due to shear. This type of failure is catastrophic because no visible signs are shown prior to failure.
How is punching shear stress and code check determined?
It is these combined forces that are used to determine the punching shear stress and code check. The direct punching shear demand is not exactly just the axial force in the Pedestal/Post. The area within the punching shear perimeter loading is assumed to pass directly into the support, so that force must be discounted.
How to calculate punching shear in footings-Quora?
The calculations of punching shear dealt in the design is based on the punching shear force that is punching against the thickness of the slab or foundation. This can happen only if there exists shear alone in the system. This is not possible if there exist any form of moment in the pedestal or the column.
