Dry rot could be factor in Berkeley balcony collapse, engineers say

The wood was so deteriorated at the balcony site that when workers on the scene touched the wood, parts of it broke off, said Darrick Hom, president of the Structural Engineers Assn. of Northern California and an Oakland structural engineer for Estructure, who went to the scene Tuesday afternoon.

“It was decayed. They were touching it with their hand and pieces were coming off. Obviously, if you touch a wood beam on your deck, it should not come off in your hand,” Hom said.




Read more at:
http://www.trbimg.com/img-55808e31/turbine/la-me-ln-dry-rot-could-ve-contributed-to-berke-001/750/750x422

...

“It appeared to be shredded and darkened and had all the appearance of wood that had been totally compromised by dry rot,” he said.

The balcony itself should have been able to support the weight of 13 or 14 people, he said.

“If you had 14 people, and they were all -- I don’t know -- football players, and they were jumping up and down, you would get a fair amount of deflection, depending on how well the railing was tied back,” St. Onge said. “But if the [wooden supports] were designed even under minimal standards, it should still have held.”

...

There are other clues that the wood had rotted. There is visible mold in one of the broken wooden joists. And it broke into short fibers at the failure point, a sign of dry rot; if the wood had not rotted, “you would see long slender splinters. It would look like a broken baseball bat,” said Bernard Cuzzillo, a consulting engineer who has a doctorate in mechanical engineering at UC Berkeley who visited the balcony scene Tuesday.

And when you look at what used to be the floor of the balcony, much of the wooden joists that once supported it have disintegrated.

Cuzzillo offered his interpretation of what happened:

The seven horizontal wooden joists that supported the balcony broke. The deck folded straight down 90 degrees, while the guardrail assembly flipped upside down.

.

“And the very startling thing is that only remnants of the joists remain in those locations,” Cuzzillo said. “You’re basically looking at what had been the joists, lined up now vertically, and now mostly gone, because they’re rotten. So basically, almost all that’s left of the joists are its shadows.”

Added Cuzzillo, “It became degraded over time due to dry rot. But then it completely disintegrated in the incident, in the fall, when it broke off.”

http://www.latimes.com/local/lanow/la-me-ln-dry-rot-berkeley-balcony-collapse-20150616-story.html#page=1