What is punching shear failure of foundation?

Punching shear failure of foundation occurs when there is a localized force acting on the structure. It is mostly found in foundations but also common in flat slabs.

In punching failure of foundations, the column breaks through the foundation mat. In flat slabs, the failure occurs at the column head. This type of failure is sudden and does not show any warning. Therefore it is crucial to check for punching shear and to provide sufficient reinforcement to take care of it. Reinforcements should be provided in addition to the main reinforcements. This punching shear must not be neglected though it is less critical than the beam shear.

To know more about punching shear,

https://theconstructor.org/structural-engg/punching-shear-slabs-foundations/17716/

The kind of reinforced concrete slab is a punching shear that is governed by high localized force. In the case of flat structures, this happens at column support points.

https://theconstructor.org/structural-engg/punching-shear-slabs-foundations/17716/10

A simplistic phenomenon where a concentrated force on a slab causes a shear failure cone and that “punches” is called a Punching Shear.      For determining maximum punching shear stress, the applied shears and moments, along with the shape of the punching shear failure cone, are utilized.

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Punching shear failure is a type of failure occurs in a soil of very high compressibility. This type of failure is characterized by very large settlement. This type of failure mostly found in flat slabs.

The causes of punching shear failure are as follows :-

– Poor drainage. Some examples of poor drainage include short downspouts clogged gutters , or lack of waterproofing.

– Weather conditions

– Poor soil conditions

– Transpiration

– Poor building site and ground preparation