Portal frame

Steel portal frames are capable of spanning large distances. They are used in the construction of factories and warehouses, and other low-rise buildings that require wide spans. Wall and roof bracing is normally provided in selected bays, often at the end of buildings. Additional vertical column or beam sections may be introduced at the gables (wind posts) to support cladding on end walls.

Roof beams (rafters) and columns are usually fabricated from rolled steel sections, while purlins and cladding rails are usually in light steel sections. Liner trays may be used as an alternative to cladding rails.

Cladding materials include built-up cladding systems (as shown), composite cladding panels, and masonry.

Small single storey industrial buildings can also be constructed using light steel sections for the columns and rafters

Approximate structural sizing

ROOF BEAMS (RAFTERS)

Typical span = 20-50 m

Beam depth = Span/60

Cold formed rafters span up to 18 m

COLUMNS

Column depth = 1.25 x roof beam

Width = as UB sections