How do I add wind loads to a portal frame in CalcSteel?
Common Scenarios
Wind loads on a portal frame have two components: external pressure on windward walls, leeward walls and roof (suction), plus internal pressure (depends on building openness). In CalcSteel, you create a new load case (e.g., "Wind +X"), then apply distributed loads on each surface with signs and magnitudes computed per your wind code (NBR 6123 for Brazil, ASCE 7 for USA, Eurocode 1 Part 1-4 for Europe). For a typical portal frame 12 m wide, 6 m tall, basic wind speed 35 m/s: windward wall pressure ≈ +0.7 qz, leeward wall ≈ -0.3 qz, windward roof ≈ -1.1 qz (suction), leeward roof ≈ -0.6 qz. The load combinations then combine wind with dead and live loads per your code (1.4D + 1.4W, 0.9D + 1.4W, etc.).
Key takeaways
- Wind codes (NBR 6123, EN 1991-1-4, ASCE 7, IS 875-3) all reduce wind to a velocity pressure q times pressure coefficients on the windward, leeward and roof faces.
- Net pressure is (external Cpe minus internal Cpi) times q, and internal pressure must be analysed both positive and negative.
- NBR 6123 got its first revision in 35 years in December 2023; ASCE 7 shifted to a 3-second-gust basis in the 1995 edition (ASCE 7-95) and to ultimate wind speeds in 2010.
- In CalcSteel you build the frame, create one wind load case per direction, convert (Cpe - Cpi)q into line loads via tributary width, and add the 0.9 DL + WL uplift combination that controls a light frame.
Full guide
Wind Loads on a Portal Frame: Step-by-Step
Step-by-step with figures and sources — 10 min read
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