Residential Deck Collapses in NC - 21 Injured
Residential Deck Collapses in NC - 21 Injured
(OP)
This article is about a deck that collapsed, injuring 21 people. From a strictly engineering viewpoint, looks like evidence is growing that the copper based treated lumber (ACQ), one of several treatments that replaced arsenic based compounds (CCA) about 10 years ago, may be expediting fastener corrosion. This has been known all along but, unfortunately, may take incidents like this to "prove" it. Time will tell.
http://www.charlotteobserver.com/2013/07/10/415664...
http://www.charlotteobserver.com/2013/07/10/415664...






RE: Residential Deck Collapses in NC - 21 Injured
"Peter Combs, an Atlanta-based architect who has testified in more than 90 court cases involving structural integrity, said Wednesday that in most deck collapses, the problem actually is with the connection between the deck and the house."
Does anyone see anything wrong with this picture? This guy is dangerous...
Mike McCann
MMC Engineering
RE: Residential Deck Collapses in NC - 21 Injured
http://awc.org/helpoutreach/faq/faqFiles/Corrosion...
another from the North American Deck & Railing Association:
http://www.nadra.org/acqarticle.html
... in this case, looks like the newspaper article MAY be correct. As I said in the original post, "Time will tell."
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RE: Residential Deck Collapses in NC - 21 Injured
There is usually not a single cause, but multiple errors...most commonly, poor construction...but could be poor design or lack of design altogether. As for fasteners, corrosion will occur in exposed decks without regard to the treatment. Any copper-based treatment will exacerbate corrosion of steel nails/screws...at the ionic level, they are dissimilar metals. The rate of corrosion has numerous variables that are often site specific. Increased moisture, increased chlorides...all lead to corrosion.
RE: Residential Deck Collapses in NC - 21 Injured
Mike McCann
MMC Engineering
RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
I just thought....90 times testified??? How old is this guy. I've been doing this a long time and it would be difficult to fit in 90 testifying events since the pace of construction litigation is so slow.
He's an architect! What are his qualifications to opine on structural integrity? Yes, I know architects are allowed to "design" structures up to a certain limit, but that usually does not involve anything rigorous.
We do have to consider; however, that he's a Gator! (Go Gators).....he can therefore leap tall buildings in a single bound.
RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
Many Engineers, Architects, and Contractors are going to need "re-education" into the details and importance of correct fastener usage.
In coastal areas hot-dip galvanized fasteners are common because of seawater and "salt-air" corrosion. Is hot-dip common on more inland areas?
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RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
"Marzano said 25 people were on the deck when it gave way.
“I do not think the N.C. building code anticipates 20 to 30 people in a small deck at one time,” she said. “It happens often for photo ops with large families at the beach.”"
25x150lbs average / 60 psf = 62.5 sf >> 6x10 deck or so. Article says "small deck". Anyone know deck size?
But what has always concerned me is that same 25 people crowded together on the edge of the deck jumping up and down excitedly, same as msquareds rhythms above, occupying maybe 1.0 to 1.5 sf per person, generating 100 to 150 or more psf live load locally.
RE: Residential Deck Collapses in NC - 21 Injured
Do architects wear black to match their minds or their hearts?
RE: Residential Deck Collapses in NC - 21 Injured
Do architects wear black to match their minds or their hearts?
RE: Residential Deck Collapses in NC - 21 Injured
Mike McCann
MMC Engineering
RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
I did a report on a deck collapse about 15 years ago. The backyard sloped away from the house and there was a ravine below which increased the height of fall... several people were injured and a few hospitalised.
The deck was horizontal and the 3'6 guard were all around, except for the area where the stair and an enclosed area existed. The deck was elevated about 15' and braced back to the building at the base; the sloped brace was on an angle about 6' hor and 15' vertical. The deck had never been loaded as heavily; there was a fairly large international crowd. The deck had been used with light loads for over 20 years...
The large number of people put a horizontal outward load on the fasteners to the wall. These failed in 'pullout' and as initiating slip occurred, the horizontal force increased, precipitating failure. There was a minor trace of dry rot (brown rot). As the sloped brace rotated, the horizontal force increased, and precipitated the total failure. It was a total collapse, the deck load was pretty much distributed over the area.
If the outer supports for the deck had been vertical, there would not likely have been a failure.
Dik
RE: Residential Deck Collapses in NC - 21 Injured
RE: Residential Deck Collapses in NC - 21 Injured
Dik
RE: Residential Deck Collapses in NC - 21 Injured
The lawyers are going to have another big paycheck.