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Non-Conventional Gusset Plates - What's Next?
The attached powerpoint presentation photos demonstrate roof/ceiling trusses constructed without conventional gusset plates or other hardware. They appear to be constructed with glue. I do not know if any studies have been conducted on this type of assembly under fire conditions, but it is worth to consider, because even trusses constructed with standard gusset plates have been shown to fail in as little as 4-5 minutes under fire conditions. These trusses were found in New Jersey and would not meet California Building Codes as of now.
Be aware, low cost, light weight construction continues to gain acceptance in the building community, at the expense of durability under fire conditions.
TCSS, Mike Schlags, Santa Barbara, CA, USA
mschlags@yahoo.com
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Permalink Reply by Ben Waller on
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If high-heat glue is used, they hold together OK...at least up to a point.
The gusset plate problem is that the gussets don't penetrate the wood much.
When the wood starts vaporizing, it takes very little wood loss to have the gussets lose contact with the wood and the trusses fall apart.
Glued trusses have a much larger contact surface area, so it takes more wood vaporization to make the trusses fall apart...as long as the glue is heat-resistant.
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Permalink Reply by Lawrence W on
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The problem is, IMHO, that you just don't know what construction method was used for the particular structure at the time of a fire emergency. Best to plan for the worst and hope for the best, particularly with new construction.
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Permalink Reply by T.J. on
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That don't look good at all, and it's not going to be found in Michigan with our building code either!
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Permalink Reply by Mike Schlags (Captain Busy) Retd on
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do you have access to any of the testing data? or a weblink?
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Permalink Reply by Kimberly A Bownas on
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Most of the glues being used are not necessarily high-heat glues and so in there lies the problem. We are now having to guess on whether the appropriate application was used when the trusses were built. This is such a huge problem because of the fact that manufacturers are looking at cheaper and they think it is better. Not for us it isn't. This is were in my forum about light weight construction I was saying that we need to rethink about going on a roof to ventilate. This is so much a matter of safety for us and also in whether we really need to go in. If the roof is unstable what about the rest of the structure. They aren't just making the trusses cheaper they are also making floor joists cheaper as well. In this day and age we need to rethink how we fight fires. Things are changing and it isn't always for the better, especially for the fire service....
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Permalink Reply by Cory on
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Let me do a little research, Chicago Fire an UL have been doing studies on stuff and I'm pretty sure if I remember correctly that they showed a floor with that type of construction that they tested and I didn't think it was very effective. It might take a few days but let me see what I can find, I took a class up in the north side of Chicago a couple of months ago with a lot of different teachers it was a 2 day deal. I'll send you a friend request just in case I can't find this blog in a few days.
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After ripping my house apart to find my notes from the class I did find the email I needed just for your information I'm going to post it so you can send him any questions you might have. Chicago fire is working with UL to find information and test anything that needs to be tested so if you have any idea's you probably can talk to this guy and get something started.
James M. Dalton
james.dalton@cityofchicago.org
(312)747-7236
Office of Research and Development
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Permalink Reply by Brian Dumser on
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"Glued trusses have a much larger contact surface area, so it takes more wood vaporization to make the trusses fall apart...as long as the glue is heat-resistant." - Ben Waller
That sounds logical. I haven't seen these in Illinois yet, but they sound like a good alternative to gusset plates.
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Permalink Reply by Christopher J. Naum, SFPE on
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Finger Joint Truss systems have been predominetly used in residential and multiple occupancy structures on the East Coast since the early 1990's. These like other Engineered Systems require an acute understanding of how they are being used within a given occupancy, the method(s) in which they provide structural support and the potential impacts during fire operations. They require the same respect in incident command management and risk profiling. If these are popping up in your jurisdiction, you need to get into these structures, observe and prefire plan. Attached is a reference document. In addition, the IAFC Safety, Health and Survival Section is working closely with UL on on-going systems performance testing on various engineered systems.
Here's a link on testing info.....http://www.carbeck.org/fingerjoint.php - Attachments:
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Permalink Reply by ECB on
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I'm curious as to how the Michigan Code will prohibit them? Do you use the International Residential and Building Code? I am very familiar with them, and am not certain how they would do so. Is it a State modification?
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One of the things we do in New York State is mandate that a number of occupancies label the building with the type of construction. This is the link to the web page that describes the signage and location. You wont know if its glued or plated, but you will have an idea of the construction type.
http://www.dos.state.ny.us/code/part1264.htm
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More test date; Here's a link on testing info.....http://www.carbeck.org/fingerjoint.php
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