# 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,
For in-plane effects the effective thickness is:
For bending effects the effective thickness that gives an equivalent second moment of area is: