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Update: Boston’s Big Dig Still Has Engineers Talking
Elizabeth M. Taurasi, Managing Editor -- Design News, August 9, 2006
Four weeks after Boston’s Big Dig succumbed to materials failure, there have been many changes to the infrastructure - from investigations into who is responsible, to stripping of all epoxy bolts from the city’s tunnels. But one thing has remained the same - engineers are still talking about it.
When the July 10 accident occurred, spurring an investigation and a full federal review of the project, blogs and forums were popping up all over the Internet where engineers and contractors alike were offering their opinions under the guise of anonymity. Hundreds were online offering their two cents from the day the news broke and they continue to do so today.
One difference – current conversations are more about how much of a screw-up this project is being perceived as, along with more speculation as to why parts of the project were assembled the way they were.
Just this week, the Boston Herald reported that all the epoxy bolts, like the ones involved in last month’s fatal tunnel collapse, have been removed or replaced with stronger hardware. Some ceiling panels have been removed all together, while others have been reinforced with stronger anchor bolts.
Yet, while some are hitting the Big Dig hard with their thoughts on just how poorly it was built and designed, others are still debating the materials used to hold the concrete ceiling panels in place.
Others are talking about how they think the investigation will go – and discussing everything from the type of epoxy used, who supplied it, and how it’s all going to play out in the end.
At Universal Hub, a Big Dig Debacle blog is spurring conversation, complete with the latest news updates and links to other blogs where there are discussions among engineers.
Dvorak Unsensored, one of the first blogs to cover the Big Dig mess, continues to stay on the topic as the situation worsened. Beyond the money, the wasted time and effort and the traffic mess, they believe the real damage lies in the “betrayal of trust of the public. That is the biggest failure,” it says.
“What I cannot understand is why anyone felt the need to hang huge, heavy concrete panels from the roof of the Big Dig,” says one reader. “Apparently they play no structural role. Quite the opposite, they stress the roof. If the designers thought the natural stone roof unsightly, why not cover it with lighter (plastic?) panels? And of course I think back to the Romans, who solved this problem millennia ago with the Roman arch - which is self-supporting and cannot fall.”
Another reader, who says he works in architecture with epoxy-embedded bolts from a company called Hilti, says an expansion bolt should never be used to hang something from a ceiling.
“It relies on gripping the material that surrounds it, which may not be all that strong or durable for a dead weight in tension (as opposed to a toggle bolt, which has mechanical wings to grip the opposite side of the material). Epoxy glue has such a reputation for being ‘stronger than the material it’s gluing to,’ and it certainly is hard stuff if you mix it and prepare the surface properly, but one wonders if some folks get a little too confident in that. It apparently weathers, too (like concrete).”
Certainly in the weeks and months to come these conversations will become even more interesting, especially as we find out more details as to what happened, why it occurred and who ultimately will be responsible for the damage and death caused by structural failures in the $14.6 billion project.
Read the original article, Boston’s Big Dig – One of Engineering’s Biggest Mistakes?
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