Steel portal frame warehouse designed to Eurocode principles

Havelland Logistik is building a single-storey distribution warehouse near Magdeburg for parcel sorting. The building is 60 m long and 30 m wide, with a clear span and no internal columns, because the sorting conveyors need the full floor. Eaves height is 8.0 m for racking, the roof pitch is 6°, and there are 11 portal frames at 6.0 m centres. The roof carries a lightweight insulated panel, PV panels over half its area, and sprinkler pipes and lighting.

The design-and-build contractor's first scheme came in at 41 kg of steel per m² of floor area, and the client's cost consultant thinks 30 to 35 kg/m² is achievable for a frame like this. The contractor wants a second design from you that is lean but safe, before the steel order is placed in five weeks.

You will design to the principles of EN 1990, EN 1991 and EN 1993-1-1, using the German national annex values for snow and wind where you can find them, and stating any value you assume: - a design basis with permanent, imposed, snow and wind actions and the combinations; - an elastic frame analysis, with a check of whether second-order effects must be included; - member checks for the rafter and column, including buckling with the restraint from purlins and stays; - the eaves haunch, apex connection and pinned base; - purlins and the wind bracing system; - a steel tonnage, general arrangement drawing and cost estimate.

Done means every member and connection passes with the governing combination shown, the frame stability is checked, and the tonnage is compared with the first scheme with a clear explanation of where the saving comes from.