Consider a simple building with the following parameters:

Building is to measure $12m$ wide by $14m$ long, with columns located at each of the four corners. Beams are to be spaced at $2m$ on$-$centre.

Building is intended to be a small shopping mall located in Windsor, Ontario.

The roof of the building is flat. The roofing material is a flexible, elastic rubber membrane. The ceiling material on the underside of the roof is a brittle plaster that is susceptible to cracking.

Weight of all permanent components supported by the roof steel $($including the weight of structural steel itself$)$ has been estimated to be $1\mathrm{.}2$kPa $($unfactored$).$

Specified $($unfactored$)$ snow load for the roof is equal to $2\mathrm{.}8$kPa per NBCC requirements.

The architect has requested that wide flange beams no deeper than $610mm$ be used on the roof, though that requirement does not apply to roof girders.

Using the loading information provided to design the roof of the building as follows:

Select a steel wide flange roof beam, with depth not exceeding $610mm.$ Assume the steel roof decking provides continuous lateral support for the top $($compression$)$ beam flange.

Select a steel wide flange roof girder. Assume that roof decking does not brace the girder top flange. Instead, brace points are provided for the girder at each of the beams connecting to it$.$

Note that $($for simplicity of analysis$)$ loading on the girder can be considered as uniformly distributed based on the girder's tributary area, rather than considering the point load end reaction of each individual beam.

Deflection requirements can be ignored for the roof girder.

CISC Part $5$ tables may be used for design$/$selection of roof beam & girder size.