Wind suction and mixed fasteners

[SteelPE]

I am in charge of designing the metal panel for a project in a 140mph wind zone. The metal panel is going to be supported by lt guage girts at 4’-0” o.c. I am currently trying to design the attachment of the panel to the girts. I can use 2 types of fasteners, a joint fastener (#14 T3 screw) and a “back fastener” (Fab-Lok). Joint fasteners are always used to join two panels together. When the loads become too great for a single joint fastener, a back fastener is used. I have the allowable capacities for both joint fasteners (464#) and back fasteners (153#).

On an equivalent 2’-6” wide panel I have a suction of 731#. Is it appropriate to add up all the capacities of the fasteners that act on the 3’-6” wind panel and make sure they are greater than 731# (1 side fastener and 2 back fasteners 770#) or do I have to apply the wind loads to each fastener based upon their tributary area (apply 1 side fastener and back fasteners at 6” o.c.)?

 

[JedClampett]

ASCE 7-05, Section 6.2, says you have to design based on an area tributary for each fastener. That probably is meant just to define the Effective Wind Area, but I would use it for both. Fasteners are very unforgiving on distributing forces.
Another thing to consider is that for a continuous member, like a panel, the interior supports see slightly more force based on the tributary areas, than the ends.
And are your panels 2'-6" or 3'-6"?

 

[SteelPE]

Thanks,

I thought I was going to have to space the back fasteners at 6" o.c. on the back side but I wanted to make sure I wasn't being to harsh on the client. I have been told that the panels are 42" wide, so this is what I am using. If I tell them to apply the "back fasteners" at 6" o.c. in-between the joints I guess it doesn't matter how wide the panel is.

In terms of girts..... I was given a minimum girt size to use and I am only stressing the girts about 60%. In this instance architectural requirements are governing the design.