Punching of hollowcores, according to EN1168

Input geometry

Element

The punching is only available for hollowcore elements.

Settings

In order to activate the punching calculations, verify that the checkbox in Calculation settings is checked.

punching settings.png

If more than 50% of the load is acting on a outer web of a hollowcore at a free edge, a reduction should be applied. Resistance should be divided by a factor of 2. Check "Reduction due to free edge" to apply this reduction.

examples of free edge.jpg

Examples of load on free edge, without and with structural topping.

Input loads

Point load-function has an option to Add loads with:

  • b: Width of load (or base plate where the load is acting)
  • e: Eccentricity of load, if it is not acting in the center of gravity.

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Results

There are a few questions why the moment curve might look strange with these kinds of supports. And the answer is quite simple. The major contribution is the effect of the prestressing strands, but also take into account that the effects of creep and shrinkage, maybe a better concrete grade, and the optional effect of a topping, changing the stiffness will contribute to a change in the deflection of the element.

If the beam would only have normal reinforcement, not prestressing strands the curve would look different:

The difference is basically the prestressing force times the distance between the center of gravity and center of prestressing force.

J
Joakim is the author of this solution article.

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