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RE: Hyatt Regency Collapse (was:E: Plan Check (was Re: Rigid Wood Diaphragm?)

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Treading carefully here to not name names and give any hints of who the parties involved were,  I would mention 3 cases that I know about. They may not qualify as horror stories and may not have saved "thousand of lives!",  but big enough of issues that can shed some light on what role a plan checker plays in the process.

1- A high-rise in southern California; during the process of plan review I noticed that it violated a section in seismic design of steel for braced frames. The section requires that no more than 70% of all braces in a given line of resistance shall resist the lateral loads in compression. The intent is that if the compression braces buckle, you would not have to entirely rely on the post-buckling compression capacity of the braces. It happened that all the braces throughout the height of the building were in the same orientation, hence would be in compression simultaneously. The steel was already ordered for the project! So, to solve the problem we came up with a compromise of verifying the adequacy of all braces for (3R/8)  (approximately 2.5) times the design loads [This was later codified in UBC (exception to 2318.8.2.3)]. They ended up having to bump up the size of several members. 

2-The other case was a very large public assembly facility that violated the weak story criteria under the vertical irregularity provisions of the code. The ground floor had substantially less lateral capacity compared to the second story. The same approach (3R/8) was used to resolve the issue. 

Both of these buildings were designed by very large reputable firms, and I have a lot respect for the engineers of the record. But, they happened to overlook such critical items, and were thankful that we caught them. 

3- Te last one was a project plan checked by another engineer whom I respect. It got substantial press coverage in LA Times after the Northridge earthquake. It involved  a very large multi story parking gagarge that experienced a spectacular collapse. The concrete buildings utilized exterior moment frames on the perimeter and a purely gravity precast system in the interior. It is speculated that apparently the building experienced substantial drift and the interior members, not detailed properly, could not go for the ride,. The project plan check engineer during the course of the review was so unhappy about the design that refused to sign and approve the plans. And, his supervisor ended up approving the project in the end.

Ben Yousefi, SE
Santa Monica, CA

>>> clifford234(--nospam--at)yahoo.com 10/16/03 12:22PM >>>
I'll bet there are some good structural plan checkers
out there who have saved a thousand lives over the
course of their careers. The thing is, when they catch
big mistakes during their plan reviews the public
never knows about it - unless they keep a "blog"! I
get the feeling however that there aren't too many
people out there who would find a plan checker's blog
interesting reading!

I'd like to hear some "horror stories" some of these
people can probably tell! 

Cliff Schwinger



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