![]() Working in New Zealand, thinking of my snow covered home. I would advocate than anyone wanting to pursue removing fly-bracing by this method get a paper on the topic to ensure they're confident with it.Īll of that said, you're almost certainly not going to get away with it in CFS It's just too unforgiving. That said, the gist of the idea is that if your purlins are greater than half the depth of your rafter and connected to cleats passing across the top of your section with two or more bolts and full depth stiffeners are provided each side of the web, you have effectively restrained the section. If you include an eaves overhang dimension, the calculator will incorporate the extension of. The computation includes results for the hip/valley factor, slope factor, and the roof slope in degrees. I posted the HERA research findings in an earlier thread, with a fairly detailed explanation. This online rafter calculator helps you calculate rafter length based on the roof slope ratio in inches per foot and the width of the building. All you have to do is input the span of the beam, the magnitude of the point loads, and their distances from support A.At first, you will only see fields for two loads (Load 1 and Load 2), but once you enter a value for x 2 small x2 x 2, the fields for Load 3 will show up, and so on. Hokie is right to take issue with your approach Statiker, as you may be effectively restraining the CFS rafters agains LTB, but you will now have another failure mode governing, likely local buckling. Our calculator is easy and simple to use. RE: Rafter unbraced length problem RobertEIT (Structural)Īctually Statiker's position has some validity, but is much more safely applied to steel portal frame rafters with stiffeners and pulins running continuously across the top flange. What are you guys thoughts and suggestions? ![]() On the other hand, this existing roof has already stand there for over 20 years without any problem according to the contractor. But to me, these soft and flexural material can not be relied on as an bracing member. See the detailed instructions below for any further questions. But the contractor says it is un-necessary to add this bracing member and he showed me an existing workshop roof which is near exactly the same rafter span except it does not has the bracing member.Īcoording to my calculation with unbraced length =48" will definitely not be able to meet the required strength, unless the designer of that existing roof considers the top felt and a thin steel roof sheet have the bracing function to the 10JWE12 cold formed steel rafter. Enter the value for the roof width (outside to outside) in feet, inches, and fraction, inches and fraction, or use the inches box to enter a value in decimals if that is your preference. Distance Details The distance between metal roof purlins depends on several factors, including the type of metal roofing, the snow load in your area, and the spacing of the roof framing. In my design I would add one bracing member at middle of the 10JWE12 cold formed steel rafter to reduce the unbraced length of the rafter to half(12') based on required flexural strength calculation. I designed a flat roof structure for a workshop in a 40psf ground snow area, lower portion in attached pdf file shows part of the roof design plan view. ![]() (basically take a hole saw, saw in about 1/2 inch, and put about a 7/8 inch long section of pipe/like in that hole saw cut).We got a difficult issue with our current design vs. ![]() ![]() Not saying your not pushing the modern limits of construction, but if you have enough 2圆's one could double up a few one on each side of the existing rafter, or as far as shear, if your concerned, could consider a split ring type of attachment, I have buildings with 2x4 on 24 spanning 12 foot, slight sag after 90 years,Īnother building 2x4 24 on center spanning 10', no seeable sag, 70 years,īarn lean to sheds, 2圆 24 oc, 15 foot, span slight sag it is 105 years old, (all lumber is Douglas fir)Īll have approximately the same slope as your drawing, all of my buildings are 1x sheeted and have been shingled, with asphalt shingles, the barn is sheeted but tinned now, ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |