AISI S100 R-factor & Panel type

[LQQD]

Hi all!

I am checking a cold formed purlin to AISI S100-16 specification and I am having some trouble to determine if my situation is covered by the specification. On determinig R-factor, section I6.2.1 refers to "Through -Fastened to Deck or Sheating". The roof panel is an insulted panel composed of a 4" thick isulation between to steel sheets, as in image attached.

Does anyone know if this type of panel is to be considered in the scope of the specification? I'm having trouble identifying which type of sheating is being considered. If not, do you know how to approach this particular design accounting for pannel torsional restraint?

Thanks!!

 

[ash060]

It doesn't look like it falls within the conditions specified in the code, since it is a sandwich panel and not a steel sheet. These look like concealed panels so the girt screws would not go through the whole panel. It looks like the code allows testing if it walls outside the given parameters, so maybe the supplier can let you know if they have done testing.

I am not aware of an approach to check if the panel-to-girt connection is satisfactory to use this section of the code. Perhaps a midspan brace can be added to the compression flange (suction case), and the unbraced length would be low enough to get you girt to work. Also upping the gage would help a little, since you are only looking at the unbraced length between inflection points.

 

[ajh1]

The panel is not consistent with the panels tested to develop that provision in the Specification. That said, the rationale behind the rib dimensions was to insure an appropriate minimum bending stiffness for the panel as the flexure of the panel coupled with the connection fastener to the purlin is what gives the lateral support to the inside (unbraced) flange of the purlin during uplift. A 4" thick double-skin insulated panel could easily be shown to have a greater stiffness than a basic R-panel with 1.25" ribs on 12" centers. The more problematic criteria is the requirement for fasteners between the purlin and panel on no more than 12" centers. If you only fasten at the seams of the insulated panel you would not meet that criteria. You would need to fasten the inside skin of the panel to the purlin on a spacing not to exceed 12". Since the fastener is inverted from the normal condition, i.e., the pull-out resistance is based on the thin panel sheet thickness rather than the thicker purlin, the recommendation would be to use some sort of a lock rivet or other fastener that does not depend entirely on the screw threads to resist pull-out. Insulated panel manufacturers generally have some sort of more intensive screw pattern designed with their panel to resolve uplift / wall suction issues for the panel itself.