Design Flaw???

[The Dad Fisherman]

This morning on the news they were reporting that the designers of that System and the Architects were battling about this design back in 1999. Any Bets that the Designers have some connection to the Board that was in charge of the Big Dig and the Architects were "Pressured" into using that system.

[Clogston29]

For point 2, I think its for waterproofing. If there was a bolt all the way through the concrete water would find its way between the bolt and the concrete and break down both the steel and concrete resulting in ceiling leaks and structural problems for both the hangers and the tunnel roof. I know that on bridges, codes do not allow for bolts to extend through the deck, I assume the code for tunnels is similar.

From what I've heard and seen on the news, it seams like there was either a flaw with the anchor system design or just poor installation. The factor of safety is very large, I want to say around 4, on tension hangers like that so something has to be really wrong for them to fail. No epoxy definately is something really wrong.