Boston big dig - what do those concrete ceiling tiles do?

I saw a diagram of the tiles that killed that poor woman in the big dig and they’re bolted to the top of the tunnel. What good do these do? Are they structurally necessary to keep the tunnel roof from collapsing?

The facts are still coming in, and you can read a lot of them in the other threads devoted to this Big Dig tragedy. Apparently the ceiling blocks are supposed to help define an air passage. The designers wanted it to stay stiff and rigid under heavy airflows. One way to do this is to reinfoce and brace light metal elemts. Another is to use heavy thick elements (See David McCulloch’s book The Great Bridge on the importance of heaviness as a stabilizing factor in large engineering projects)

Not knowing more about it, it seems screwy to me – why not construct your air tunnel separately? Why not supprt the elements, even if heavy, on load-bearing supports, rather than hanging them ptrecariously from bolts held in with epoxy? But it’s outside my expertise, so I’ll leave it to the experts.

I’m giving this one little bump.

Basicaly the panels were dividers to creat another tunnel for the air distribution system. It is not a construction technec unique to the boston tunnels. In order to withstand the forces of the air above and the vibrations from the traffic bellow them being heavy was important. The other way to do the same thing would be using lighter materials but more supports to keep them stable.

Being this is MA I’d wager a guess that the decision to use concrete panels had more do do with freinds and family in the concrete business then a technical requirement for the project.

Bolts set in epoxy may have their place someplase else. Not to support heavy concrete panels overhead. Positive fastening with welded in place bolts/nuts providing positive mechanical attachment. :rolleyes: