how is the wind load at end wall transferred to roof diaphragm by MBMA standards

[qu88]

Just like regular warehouse metal building design, the end wall is often framed by wide flange steel column and rafter and rafter is often bolted to top of column. cold form Z purling is bolted to top of rafter. When wind hits the end wall, because of free span of column, half of the wind load calculated will be applied to roof diaphragm, but load path is wind pressure applied to metal panel, horizontal between column takes place and transfers the load to adjacent columns and column will transfer half the load to bottom and top . My question is: how the concentrated wind load on top of column is distributed to roof diaphragm? Will the concentrated load damage the bottom flange of rafter first before it happens? Thanks

 

[Boiler106]

i would highly recommend this book:

https://www.amazon.com/Metal-Building-Systems-Third-Specifications-ebook/dp/B00LI367OQ

PEMB's arent my specialty, but i believe the end wall columns frame into a strut that goes back into the roof plane and is tied into the 'diaphragm' with tension tie rods.

Although, i suppose, a horizontal flexural element could transfer it to the end walls, too.

 

[phamENG]

PEMBs as you've described don't really have diaphragms - at least not usually. They use discreet braces as in plane trusses to do the job, and the roof panels are typically very thin standing seam or similar. Some are heavier and have diaphragm capacity, but it's not usually the case (at least not in my experience). The load path is typically girt->wind column->end frame bent->cross bracing parallel to wind load->foundation. Depending on the size and configuration, wind direction, etc. you may have some in plane bracing in the roof taking part as well.

To answer your question about damage - not if it is properly designed and detailed for the expected loads.

 

[hokie66]

qu88,

No need to post the same question twice in such a short time. Didn't you like the answers in the other thread?