huangyhg

big dig designers asked to reduce bolts
a new enr news clip on the big dig fiasco. apparently, someone coerced the designers to reduce the number of the bolts in the connections from 4 to 2. but i know i saw the photos of the plates with 4 epoxy bolts hanging out so i don't understand this story:
reminds me of the hyatt-regency. connection...contractor submittal...
from the story:
"unless i'm missing something, i don't see why (the ceiling designer) requires a 4 bolt anchor plate when a 2 bolt anchor plate would be sufficient," robert richard of bechtel/parsons brinckerhoff wrote.
richard's memo, dated june 23, 1998 and addressed to gary baxter, also of bechtel/parsons brinckerhoff, said gannett fleming should either cut the number of bolts in half or submit calculations "proving that 2 anchor bolts do not work," the newspaper reported.
gannett fleming officials agreed to reduce the number of bolts, calculating that the ceiling would be safe "assuming proper installation and quality of the product materials," according to a company statement."
ok, so it looks like calculations were submitted proving that two bolts would work. what's the problem?
bechtel/pb and gannett-fleming aren't rookies and don't hire people who are intimidated by much of anything (it's the other way around, in my experience). if there's money to be made, they make it and if a real savings - without compromising safety - could be realized, then they are 100% within their right to make it happen.
let's see the calcs and not let the boston globe tell us our business.
be that as it may, if this turns out to really be something akin to the hyatt-regency, then their heads should roll.
no...my confusion was that all the photos i saw in the news showed plates with four bolts. here they are saying that they reduced the actual construction to two bolts.
somwhere in this forum there is a long thread on this topic with lots of links. my recollection is that there was a 20 ft tee holding the panels. near the ends of the tees were rods going straight up to a connection that had 2 ceiling bolts each. the center had one vertical and two diagonal connecting rods. this conetion had four bolts. i think they were talking about the ends.
my problem with the design is that it is difficult to install epoxy anchors overhead and acheive reliable repeatable results. my other problem is that the five points of connection all had turnbuckles, making it impossible to determine how much load was in each connection.
a very intersting topic to follow.
jae-
jmiec - i actually remmeber a photo where there were not only 4 holes, but 4 bolts hanging out of them. maybe in some cases there were two. i guess i'll keep watching the news and photos. eventually i suppose there will be a report out on the failure.

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