SIPA has finally set up a blog!!!
SIPA is beginning its “Blog” journey to bring the association’s members together while at the same time educating the public and spreading the benefits of building with SIPs. We want to use this interactive networking tool to promote education, conversation and to be able to follow the projects our amazing members are embarking on. SIPA has been in existence for over 18 years, during which thousands of buildings both commercial and non-commercial have been built. It is our desire to begin showcasing our member’s amazing work and to be able to allow members and viewers to see the progression of projects.
We hope for active participation with this and we want to hear your stories, ideas, projects and interests. We will continue to cover our member projects, industry happenings and hopefully through all of this learn, educate and have some fun.
Posted by Dennis K on October 30, 2009 at 10:03 PM
As a semi-retired structural engineer currently working as a building official I have some experience with structural insulated panels (SIP) from the perspective of both positions. I have used SI Panels as a structural engineer but am now in the position of having to approve their use as a building official. Maybe you can help and maybe you can address some of my concerns with your upcoming standards.
The current issue involves the use of SIP roof and wall elements in a building with a 100-psf roof snow load requirement. The ES Report for the panels used does not include a limitation on design. This seems true for all panels I have looked into. The drawing shows a portion of roof with a 12:12 pitch. The connections specified are only the standard connections (ie 4-panhead screws per panel into a sloped bearing block attached to the top plate of the wall). The ESR for the panels does specify that calculations for all load transfer connections must be submitted to the building official but that does not automatically happen. In fact I received the first calcs 6-months after I requested them from the engineer. The engineer has since submitted several different calculations all attempting to justify the generic detail (the roof has been built).
To begin with, limitations on applied load should be included for all prescriptive connections. Secondly, panel manufacturers must supply allowable loads for the specified fasteners. Allowables for the fasteners can’t readily be determined from the current NDS. I’ve been an engineer long enough to know that there were failures involving insulated panel roofs before the specified fasteners were changed from nails to hardened screws. The geometry of the connections put some added stress on the fasteners. Allowable loads should be determined from test data and should be made available. Currently it seems that the connection is relying on the glue but specifying fasteners to skirt the fact that ICC approval for field applied glue isn’t forthcoming.
The SIP industry should look at other systems that have wrestled with similar issues such as the manufactured joist industry. TJI currently has prescriptive details requiring straps for slope bearing conditions over a given pitch. They also include a limitation on snow load for their prescriptive connections.
In the absence of specifics in the ES Reports, I assume the prescriptive connections from the manufacturer have the same limitation as conventional light framing in the IBC. This limits the use of the panels to 50-psf ground snow load unless calculations with supporting data are supplied by the Engineer Of Record. But supporting documentation is pretty hard to come by for the screws, so you see my dilemma.