Details of punching shear

This construction video tutorial is extracted from a final year project held in 4th year civil engineering at the University Of Limerick.

In this video, brief explanation is provided on the basic characteristics of punching shear.

In this video, discussion is made on the following topics:-

Definition of punching shear

Evaluate the punching shear resistance of a component

Measures to rise punching shear resistance

Definition Punching shear refers to a brittle failure mode of reinforced concrete slabs or foundation due to shear that happens if a concentrated load is employed in a small area of concrete section. As for example columns supporting flat slab, pad foundations. At flat slab structures, it happens at column support points.

Some instances of the happening of concentrated loads on a slab are a column, specifically on a pad foundation, and wheel loads.

In case the total shear force surpasses the shear resistance of the slab, the slab is pulled down around the column, or it can be observed same as the column being punched via the slab.

Punching shear failure mechanism is seen in normal floor slabs, flat slabs, and in the foundation slabs underneath the column. In pad foundations, where weight and depth are insignificant, it’s effects are fulfilled with the arrangement of adequate depth.

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.

So, there is a diminution of ultimate load capacity of the structure underneath the flexural capacity with the action of shear. With regards to beam shear, the punching shear is less important.

In slabs, the punching shear takes place under the action of high values of concentrated loads. These load range from the wheel loads on the bridge slabs or the loads delivered from over floors on the columns that provide support to the slab floors.

To get more detail information on punching shear, go through the following video tutorial.

Video Courtesy : Pádraig Sweeney

punching shear