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Steel Curved Roof, diaphragm effect?

Steel Curved Roof, diaphragm effect?

Steel Curved Roof, diaphragm effect?

When analyzing a roof for wind loads, the steel deck can be used as the rigid diaphragm, when the roof is curved only in one direction, does this diaphragm effect still applies for the system?

I am using W 16x48 sections for the beams, the columns are 16” HSS, the roof is 80ft x 90 ft with max spans of 40’, the curved beam has a radius of 90ft   

RE: Steel Curved Roof, diaphragm effect?

I thought metal deck was considered a flexible diaphram.  Concrete on metal deck would be rigid.  I'm an EIT, so I could be completely wrong.

RE: Steel Curved Roof, diaphragm effect?


You are correct. You have to have concrete (as in concrete slab or concrete on top of metal deck) to achieve rigid diaphragm.



RE: Steel Curved Roof, diaphragm effect?


Although concrete would be my personal preference, diaphragm action can also be achieved with certain types of steel deck using vermiculite aggregate and rigid insulation. Also note that deck lap conditions and weld patterns greatly effect the diaphragm action.

RE: Steel Curved Roof, diaphragm effect?

You should check the deflection of the deck against the deflection of the shearwall to determine if it's rigid or flexible.  Flexible deck deflects more than its supporting shearwall.  Rigid deflects less.  I think it's the same if the deck is supported by a moment frame.  Almost always steel deck with no concrete is flexible for typical construction spans and loads.

Given proper detailing and engineering you can use the steel deck for a diaphragm even if the roof is curved.  What kid of curve is it? Does it curve in plan view?  I had a case once where I had a small building with a curved side.  I was able to cantilever the steel deck past a shear wall to pick up the curved end.  

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