Horizontal deflection limits for residential steel portal frames

[addt]

Hi,

I've been asked to design the bracing structure for a 2-story residential building. For the most part everything is fine, except I've got 2 end gable walls full of windows. Based on the numbers, I'm currently 50kN short for code compliance.

I'm going to install two portal frames to resist 25kN each, and wondering what horizontal deflection limits i should use.

Any method or ideas would be greatly appreciated.

 

[Tomfh]

If you want them to act in conjunction with the bracing they should be of similar stiffness, ie very stiff.

Also, if they’re full of glazing they’d want to be very stiff too, to prevent loading the glazing and turning it into bracing.

It’s probably better to brace those bays back to hard points if you can.

 

[MIStructE_IRE]

Portal sway limits here are recommended as h/300 for masonry and h/150 for industrial cladding.

Glazing limits should be checked with your supplier or alternatively use h/300 and get them to accommodate the movement via slotted connections etc.

 

[Agent666]

1% drift is about the limit of plasterboard bracing. Just keep in mind the portal effectively responds elastically, whereas any plasterboard linings respond at a higher ductility. Probably not relevant to your region, but this is used here in NZ to design portals in residential applications combined with other board lined walls, theory will be applicable at any rate.