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Portal Frame

Portal Frame

Portal Frame

What is the difference between portal frame with cladding surrounding 4 sides on plan and the one without in terms of structural analysis ? how do we check the lateral stability of the portal frame in the transverse direction ?

RE: Portal Frame

Its all about wind loading. A fully clad portal frame will be subject to loading, both pressure and suction, on the walls which will lead to lateral forces in the plane of the frame and the longitudinal forces will need to be resisted by bracing in the roof and walls.

Frames without cladding, assuming a roof of course, these forces will not be present because the wind will pass through. However, this situation can give rise quite large uplift forces on what is now effectively just a canopy and the frame will need more rigorous checking for stress reversal on the rafters and purlins together with uplift on the bases.

RE: Portal Frame

If the top of each column in the portal frame is connected to a roof diaphragm or other structural elements that can resist instability in the transverse direction, then your portal frame is braced top and bottom in the transverse direction.  If the above is not true, then your columns are "flagpoles" which must be fixed to their bases for transverse stability.  The beams in the portal would be braced at their ends by these flagpole columns.


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