Re: MORE TRAMWAY TRIVIA

["Ron BEST" <ronbest@bigpond.com>]

Ben Staples <98711576@student.hawkesbury.uws.edu.au> wrote in message
<7d4t0o$i5g@ob1.uws.EDU.AU>...
>
>My best guess about that tunnel question is that a tunnel is a structure
>that does not directly support any live loading, i.e. any form of traffic
or
>wind. The tunnel would only support earth which is a dead (constant) load.
A
>bridge directly supports live loading.
>
>Ben Staples
>
What if a road happens to cross above the tunnel? AFAIK, the structure
located on the main western line in Sydney between Sydney Central station
and Redfern station is officially called "Cleveland Street Tunnel" - I think
it started out life as a bored tunnel, but has been extended since. It
certainly carries plenty of live loading! (Regent and Cleveland Streets,
both with tramways at one time. )

I don't think you can make a distinction as to how a tunnel was built
(bored, cut and cover, Armco culvert etc.) I think it comes down to the
amount of cover - bridges cover whatever they cross for a relatively short
distance (e.g. the width of a road or railway line), whereas tunnels cover a
relatively long distance. So, underground railways run in "tunnels", however
built. My example above of the Cleveland Street "Tunnel" would be a bridge,
by my definition. But what about where the City Link structure runs above
the Upfield railway in Melbourne? A very long, very skewed, bridge?
Certainly not a tunnel!
Rgds
Ron BEST