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Hollow Slab

This dialog is accessed from the 2D element property wizard and is to simplify the specification of slabs that may contain voids.

Definition​

Slab thickness

The overall thickness of the slab

Thickness of top/bottom zone

The top and bottom zones are assumed to have the same thickness and the material is assumed to be concentrated in these zones.

Proportion of material in void zone

Typically the central part of the slab will have some material so a percentage can be specified here. A zero percentage will give the same results as a solid slab

Syntax​

The description of  hollow slab profile is

thick(unit) H top void%

where

  • thick – the overall thickness
  • unit – the units defining the profile
  • H – hollow slab
  • top – the thickness of the top (and bottom) zones
  • void – the percentage of the core that is void

Effective depth​

These are the effective depths for bending and in-plane stiffness calculations, based on an overall thickness, DD, top and bottom zones of thickness, tt, and proportion of material in void, vv

For in-plane effects the effective thickness is:

D^=vD+(1−v)2t\hat{D} = vD+(1-v)2t

For bending effects the effective thickness that gives an equivalent second moment of area is:

D~=vD+(1−v)6D2t−12Dt2+8t33\tilde{D} = vD + (1-v)\sqrt[3]{6D^2t-12Dt^2+8t^3}