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Subject: 
Re: My newest creation, Hell Gate Bridge NY
Newsgroups: 
lugnet.trains
Date: 
Fri, 8 Dec 2000 12:23:51 GMT
Viewed: 
1147 times
  
In lugnet.trains, Larry Pieniazek writes:
I'm not a civil, thanks for refining my critique.

In lugnet.trains, Scott Arthur writes:
In lugnet.trains, Larry Pieniazek writes:

Well, no, I'd have to categorise it as a type of through truss.

I was going to leave this, but now that you started...

I agree that is not a arch, and I expect that is was modelled on a truss.
However, I'd call it a frame as it is pin jointed (trusses, I think are
not). However, to be a frame all the members have to be in _pure_ tension or
compression (ie no bending moments). This is not the case with James’s
bridge. Additionally, the frame is statically indeterminate as it is not
"perfect". To be a perfect frame:

m=2j-3

m=the number of members
j=number of joints

If it were a real structure, I’d expect it to have considerable movement.

Basically, the problem is, it is not constructed from triangles. Despite
that, it is fit for its intended purpose, and it does look very good.

Oh, indeed, it looks nifty. It's just not an arch. I'm not competent to
comment on whether trusses can't be pinned, though.

While we are identifying arches, though, I thought Ben "April Fool" Beneke
did one, no? I can't find it at the mo.

There are others out there, I think.

{1} Durka – almost schoolboy level SE
http://www.amazon.com/exec/obidos/ASIN/0582251990/qid=976273366/sr=1-5/106-5958974-3391625

Thanks for the ref.. out of print, though. What I'd like to have is
something more like a "bridge spotter's guide"

If we are talking bridge spotting, I'll be crossing this (road) one today:
http://www.firstcity.f9.co.uk/newgallery/out1.htm

As I cross it, I'll be looking at this (rail) one:
http://www.geo.ed.ac.uk/scotgaz/features/featurefirst1053.html

Better picture:
http://members.tripod.co.uk/dougalh/movies/forthb.html

Both are about 8 miles from my office.

Scott A


with examples of all the
different interesting types and discussion of when you'd see them in use,
rather than a tome on how to analyse them... Following some refs got me to
textbooks that cost 250 USD and up!!!

++Lar



Message has 1 Reply:
  Re: My newest creation, Hell Gate Bridge NY
 
(...) Mighty Mac... (URL) (I've posted links to it in the past I think) (...) bridges that look like it in shape (with the inward sloping cantilever towers) or in expanse and it was a ground breaker in its day. My hero, D. B. Steinman, (1) took a (...) (24 years ago, 8-Dec-00, to lugnet.trains)

Message is in Reply To:
  Re: My newest creation, Hell Gate Bridge NY
 
I'm not a civil, thanks for refining my critique. (...) Oh, indeed, it looks nifty. It's just not an arch. I'm not competent to comment on whether trusses can't be pinned, though. While we are identifying arches, though, I thought Ben "April Fool" (...) (24 years ago, 8-Dec-00, to lugnet.trains)

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