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Re: Berkeley balcony collapse leaves 6 students dead

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Very sad and preventable. But they said the building was fairly new and it
looked like it was newer architecture and just judging by the finishes,
which makes it a bit more surprising.

I would bet this is water intrusion and decay damage more than overloading
(but I reserve the right to be wrong) , even though it had what sounded
like a significant occupancy at the time .

I do a lot of forensic engineering, and have seen a lot of balconies, decks
and roofs with similar water intrusion problems at the framing member to
wall junction. This is especially an issue down here in Florida due to our
frequent thunderstorms, wind blowing rain onto the balconies, and then the
heat and humidity are a perfect environment for fungi to thrive. I know San
Fran can be pretty wet also, just not as hot. But envelope and
waterproofing design there would be fairly critical in wood framed
structures.

The insidious thing about wood-framed balcony/deck deterioration, if it
occurs at the wall-balcony joint, the occupants/owners/maintenance
personnel may never know until there is a really bad problem or a failure,
as the balcony stringers are slowly rotting away inside the wall and nobody
knows. With such a short span you wouldn't likely get a lot of deflection
as a warning, and normal loading is probably a couple people, and then one
night you have a party and you suddenly put 8-10 people on there, and you
have no idea the beams are rotten. And they are rotten at the highest
bending stress area of the beam.

It would take very little extra labor and money to frame these with 2-3
steel channels cantilevering out from the main floor structure. At least
that way corrosion would likely take a lot longer and hopefully you would
see some rust stains or something first. I know the real answer is better
envelope design and construction, better sealing, flashing, etc., and
better maintenance.

Andrew Kester, PE
Florida

On Tue, Jun 16, 2015 at 1:41 PM, Abolhassan ASTANEH-ASL <
astaneh(--nospam--at)berkeley.edu> wrote:

> The structural failure tragedy has hit students. I am sure you will join 
> me as practicing structural engineers in offering our condolences to the
> families of who perished in this tragedy and our prayer to those who have
> been injured for fast and full recovery. Apparently the building is not
> owned by UC Berkeley and is not connected to UC Berkeley in any way.
> Berkeley balcony collapse leaves 6 students dead
> 
> 
> <http://cirrus.mail-list.com/seaint-seaosc/52393947.html>
> --
> 
> Abolhassan ASTANEH-ASL, Ph.D., P.E., Professor
> 2013 Minner Faculty Fellow in Engineering Ethics and Social/Professional
> Responsibility and
> 2013-14 U.S. Fulbright Senior Research Scholar
> Department of Civil and Environmental Engineering
> 781 Davis Hall,  MC 1710
> University of California,
> Berkeley,  CA 94720-1710, USA
> Web: www.ce.berkeley.edu/~astaneh

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