# Punching Shear Calculator

The SkyCiv punching shear calculator allows users to estimate the punching shear strength or capacity of a concrete slab panel. This check is also known as a 'two way shear' check. Punching shear checks are used to ensure that a concrete slab is capable of resisting forces concentrated around columns or similar structural members. A punch shear calculation checks that the shear stress at these points does not exceed the capacity of the reinforced concrete slab. Punching shear failure occurs when the shear stress in the slab concentrated around at the column exceeds the capacity. While multiple types of punching shear failure modes exist, at worse these can be catastrophic and lead to collapse. The below ACI 318 punching shear calculator allow engineers to conduct punching shear checks, with formulas and reports provided to ensure the punching shear calculations have been performed correctly.

## About Punching Shear Slab Design

## How to calculate punching shear?

To calculate punching shear, multiple steps are involved using punching shear formulas. A punching shear example calculation generally starts by determining the shear strength of the concrete. This is then followed by calculating of the nominal shear strength of the section. The governing shear strength can then be established. Subsequently, the shear strength contributed by the reinforcement is computed, along with the overall shear strength of the section. Once these values are obtained, the punching shear ratio, or utilization ratio, is determined by dividing the applied shear force by the nominal shear strength of the section. This ratio helps assess the adequacy of the structure in resisting punching shear forces. These checks should be completed by a registered structural engineer familiar with local building standards and codes.

## What is punching shear in a slab?

Punching shear in a concrete slab refers to a mode of structural failure that occurs around concentrated load-bearing points. Most commonly in structures these are columns. The punching shear failure mode occurs when the concrete slab is unable to resist concentrated vertical loads that cause excessive shear stress, leading to potential collapse.

Therefore, it is important that engineers perform shear punching checks to ensure that reinforced concrete slaves are designed to resist these loads. These checks can be completed with the above ACI 318 punching shear calculator.

## How to prevent punching shear failure?

To prevent punching shear failure the following design considerations should be taken into account by an engineer. The slab needs to be correctly reinforced by providing shear reinforcement such as stirrups or shear links around the column. The depth or thickness of the slab may need to be increased to enable it to adequately resist shear punching forces. Once these measures are in place the engineer should consult all relevant design codes and standards to ensure the structural integrity of the slab.

## Frequently asked questions

**What design standard is available?**

The American Concrete Institute's 318 standard (ACI 318-19) is used.

**Does the calculator consider two way shear capacity?**

Yes, the calculator can estimate the concentrated load carrying capacity of a slab panel. This load carrying capacity of the panel is governed by the position of the load acting on the slab panel. The punching shear design tool considers following positions of the load:

- Load acting at the interior (center) of the panel.
- Load acting near the edge of the panel.
- Load acting at the corner of the panel.

**What type of concrete types are supported?**

The calculator supports both normal weight as well as light weight concrete.

**What type of shear reinforcements are supported?**

The calculator can consider either stirrups or headed studs in the form of shear reinforcement.

**What punching shear strength cases are checked per ACI 318-19?**The following cases are checked in the Punching Shear Calculator

- Concentrated Load Transferred at the Interior of the Slab Panel
- Concentrated Load Transferred at the Edge of the Slab Panel
- Concentrated Load Transferred at the Corner of the Slab Panel

**What inputs are required by the calculator?**

Inputs are required for the column dimensions, slab dimensions, the concrete properties and the reinforcement properties.

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## About SkyCiv

SkyCiv offers a wide range of Cloud Structural Analysis and Design Software for engineers. As a constantly evolving tech company, we're committed to innovating and challenging existing workflows to save engineers time in their work processes and designs.