What does punching shear mean?

What does punching shear mean?

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.

Is punching shear the same as two way shear?

Two way shear, also called as punching shear is the type of shear failure in which a block of dimension of footing plus d/2 on either side gets punched out when the excessive load exceeds the shear force on the failure surface.

How is punching shear force calculated?

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.

Why do we check for punching shear?

Therefore we often provide drop slab/panels to increase the bearing CS, so that the reaction/shear force is distributed over a bigger area. This stress due to punching should be checked against safety.

What is punching shear in flat slab?

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 is punching shear in a 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.

What is punching shear in RCC footing?

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.

What is wide beam shear?

A beam is classified as a wide beam when the width of the beam is wider than the column width; or when the width of the beam is more than twice the beams’ height. In order to examine the shear performance, a total of six concrete wide beams were manufactured and tested.

What is punching reinforcement?

The weight of a slab supported on a column induces shear stresses in the slab. These stresses, if sufficient and where additional reinforcement is not provided, would result in the column ‘punching’ through the slab.

What is punching shear failure in soil?

Punching Shear Failure of foundation soils This type of failure occurs in a soil of very high compressibility. Failure pattern is not observed. Bulging of soil around the footing is absent. Failure is characterized by very large settlement.

What is the difference between general punching & local shear failure?

General Shear Failure – This type of failure occurs in stiff clay or dense sand. 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.

What are the three modes of shear failure?

Types of Shear Failure of Foundation on Soils

• General Shear Failure.
• Local Shear Failure.
• Punching Shear Failure of foundation soils.

What is meant by the term “punching shear”?

Punching shear is a failure mechanism when structural elements subjected to concentrated load. Failure occurs in perimeter defined away from the concentrated load. Slabs, pile caps, footings, raft foundations, etc. element is subjected to punching action and they need to be designed for it.

What is the formula for punching shear stress?

Punching Shear Stress = V/bd. Where’ V – applied force. b – length of the perimeter. d – effective depth. Punching shear stress shall be less than allowable shear stress; V

How do you find the punching shear failure zone?

Punching Shear Failure Zone for Slabs above and below the column. The ‘d’ is the effective depth of the slab. The punching shear perimeter is formed at a distance of d/2 from the edges of the column or the pedestal. In the figure-1, D ped is the depth of the pedestal.

Is design punching shear reinforcement necessary?

Design punching shear reinforcement is not necessary if v Ed ≤ v Rd, c, where v Rd, c is the design punching shear resistance of a slab without punching shear reinforcement along the control section considered. Design punching shear reinforcement is needed if v Ed > v Rd, c.