Influence of option 'Rib'

If you have modeled a slab with ribs, an option 'Rib' will appear in the properties window of the result. This option can be ticked. This is the case for the results of both the slab and the beam (rib).

The meaning of this is the following. Ticking on the option 'Rib' means that you want to show the results for the entire T-section. When deselecting the option 'Rib', the results are displayed separately for the part of the beam (rib) that hangs under the slab and for the slab itself.

In SCIA Engineer a concrete slab of 9 x 6 m with a thickness of 200 mm is modelled as an example with ribs on the mutual headway of 1 m with a section of 200 x 400 mm. The effective width that is given for the rib is 0.5 m. The load consists of a floor load of 5 kN/m² and self weight. The results are shown for the ULS combination.

The moment M_y for the beam separately (option 'Rib' ticked off, top image below) and for the entire T-section (option 'Rib' ticked on, bottom image below) is shown:

The results for the moment mx in the slab are shown below. If the option 'Rib' is ticked off (bottom image below), the moment mx will be equal to zero over the effective width because it is calculated when considering the beam as a T-section. This way the moment will not be taken into account twice.