If in the Modeler multiple deck polygons are assigned to a layout type, with some decks having the fibre option selected and others having it not selected, resulting in beams supporting some deck with the option selected and some deck without the option selected, those beams will be designed assuming no fibres. That is, if any deck supported by a beam does not have the fibre option selected, that beam will be designed without fibres.

Fibres are only considered when BS 5950 is selected as the code to be used for beam design.

For edge beams the contribution of fibres in resisting the longitudinal shear is ignored, since the code requires U-bars in that condition.