Effective Width Factor (Stiffeners, Girders as Panels)

A plate above a girder or stiffener acts as an additional flange. It increases the moment of inertia when the girder is modelled as a beam. This theoretical part of the plate which is responsible for the increasing of the moment of inertia is called effective width.

One method to take the effective width into consideration is to calculate it as a multiply of the thickness of the web plate. This factor (default 40) can be given in the idealisation options.

The effective width factor is only taken into consideration when the option Hybrid beams is selected, then the element properties are calculated around the stiffener trace line. When the option Offset beams is selected the element properties are calculated around the neutral axis. In this case the effective width factor is automatically set to 0 and cannot be changed in the idealisation settings.