Engaddict,
Hate to burst your bubble, but these shed are built in the tropics all the time, when cyclone harry crossed the cost, the rate of fail of these sheds was four times that of any other sector, the next being old houses (not designed for the wind speed). Of the engineer products, they had an 80% greater failure rate, and Larry wasn’t even a design event.
From what I have reviewed of these designs, there are a few ways the engineer justifies his design.
1. Takes moment into the base fixing, however most of these are fixed to the concrete with an angle and chemical anchors, thus rotation requirements are way too high to be considered a moment carrying connection, before failure of the frame.
2. Use the sheeting for bracing in both directions, most of the time assumed not backed up by calculations or testing.
3. Catenary Action for the design for purlins, I don’t know how people think this one works but hey why not, once you have made all the other assumptions.
4. Ignore internal pressure in region c however do not design the roller door or stays to take the wind design. The big thing here is that engineers in this area are using cold formed C’s as the door mullion. Then relying on the catenary action of the roller door, however the C-sections have no real strength in torsion, so it all goes up the creek without a paddle.
Generally form my experience you can tune a design by about 5% more from hand cal’s to computer. Anything greater than this is BS or the hand cal’s were overly conservative.
This article is a true representation of how a small group of engineers have let down the profession and the community.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
