Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

wind codes...

[Subject Prev][Subject Next][Thread Prev][Thread Next]
In FL we have no seismic or snow so we know what governs lateral wind loads, up to V=150mph. But if your building is a "simple diaphragm", enclosed, and under 60ft (95% of our projects), there are pages of simplifed tables from 90mph-150mph. The Florida Building Code is available online for free, if you guys in other parts of the country want to "double-check" your other methods of calculating pressures. Evidently, nobody seems to think this simplified method is either to conservative or too liberal for useage for the most common types of structures, which is just fine by me.
 
Do you guys in CA or out west have to submit calcs? Who knows what methods you are using as long as they are reasonable and you are getting "correct" results, if not a little overly conservative. I am just wondering what would prevent you from using an older method that you find reliable and easier to use. The only time in FL where we have to submit calcs for other people to review is on government work.... Otherwise, the plan reviewers don't really check much from what I can tell but the most basic stuff, the leave it up to the engineer to have done their job properly. Me likey this method!
 
I completely agree with Paul. For most examples he gave, and I recently read 85% of new construction in the US is 3 story and less, a simplifed version would work just fine. Who cares about 2psf? Who is this accurate in their calcs? You guys never round to the nearest KIP?  If you size a connection for uplift do you make sure you have a few extra pounds? Uplift connections from columns to concrete maybe a an extra KIP? What about when deflection/drift controls and not strength? What about the strength and reduction factors applied during steel and concrete design, adding additional safety? And many products like Simpson uplift connections, epoxy and expansion bolts, screws, etc. have an ultimate strength of 4x the allowable...
 
My point is that we are not designing things to this degree of accuracy for the most part. There is no need to be that accurate, both for design simplification and construciton simplification. The cost savings for a few bucks of steel and concrete here and there are minute compared to the costs of MEP, glass curtain walls, fancy finishes, etc, all of which offer no additional safety during a wind event (minus the glass)....
 
Making things that complicated just may create errors. I agree with Paul this time should be spend coordinating with the ARCH and MEP drawings, properly designing cut sections, details, connections, etc. In my hurricane forensics and my wind design experience, it is the smallest elements that are the Achiles Heel of a building. Plywood sheathing pulling off a roof truss, a roof truss connection failing due to improper nailing or being improperly sized, roof mtl deck peeling back, etc. It is not masonry walls failing in shear. It would rarely be a structural moment frame failing at the welds, or a braced frame buckling, or a improperly sized concrete footing pulled out of the ground as a frame or column goes tumbling down the road....
 
Just thanking my engineering gods I do not work with seismic on top of wind, or snow.... Just lots of wind and sandy soil that gets you 2000psf. Not too bad.
 
Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Ave., Suite 301
Orlando, FL 32803