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Span distance 150x50 steel tubing

  1. Oct 6, 2012 #1
    I'm designing a patio which is connected to a house on one side, 8m x 2.4m

    150 x 50 x 3mm steel tubing around the outside with 140 x 50 hardwood purlins, spaced at 1m intervals (2.4m long each).

    I would like to span the 8m with only posts on the ends. Is this possible or will there be to much sag?

  2. jcsd
  3. Oct 9, 2012 #2


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    DANger-is: With no midspan post, your given 8 m steel tube would be overstressed. Therefore, a post at the midspan of your given 8 m steel tube is also needed.
  4. Oct 10, 2012 #3
    Isn't there standards for this? You can't lookup the building codes?
  5. Oct 10, 2012 #4
    Thanks for getting back to me nvn. I'm trying to span as fare as possible withou having a support in the middle. Given that the beam can overhang the posts, I would think I could span the rhs 6.5 m between supports. Which would result in approximately 600 mm overhang on both ends. Any thoughts?
  6. Oct 10, 2012 #5


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    DANger-is: What is the material specification, and tensile yield strength (Sty), of your RHS? Assuming Sty = 275 MPa, then the maximum allowable span length between your two posts would be L1 = 5140 mm, using your current steel tube cross section size and wall thickness. This assumes your patio is no more than ~1200 mm above the ground. If the patio elevation exceeds roughly 1200 mm, then the allowable span length L1 would be less.

    Are your "purlins" (joists) actually attached to your RHS? And is the midspan of your first RHS attached to the house? Or can your joists slip longitudinally (horizontally), such that your outer RHS has no midspan lateral (horizontal) support near its compression flange?
    Last edited: Oct 10, 2012
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