Structural Engineer's Eye Candy

[IDS]

Apologies to the author of the Wikipedia article. If you zoom in on the crown in the photo in the OP (which is amazingly high resolution) you can see there is indeed a special detail at the crown, which is shown more clearly in photograph 14 from the set here:

http://bridgehunter.com/vt/windham/bellows-falls/

The demolition of this beautiful and historic structure seems yet another example of the way in which the products of engineers are seen as less important than those of architects.

I wonder if the original design calculations and drawings are filed away somewhere.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[IDS]

More photos, some drawings, and a report available here:

http://loc.gov/pictures/item/nh0001/

The photographs are available for viewing or download in high res or very high res (20 MB!).

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[hokie66]

Thanks, Doug. Looks like he had that hinge all thought out, but without a compressive force in the four chords at the hinge, I think that would have compromised the lateral bracing.

 

[BAretired]

hokie,

The lateral bracing at the hinge is not connected to the bottom chord. It is connected to the top chord and a vertical member half way between top and bottom chords, so how is the lateral bracing compromised?

BA

 

[IDS]

I have collected the photo in the OP and some details of the crown hinge here:

http://newtonexcelbach.wordpress.com/2011/05/12/bellows-falls-bridge/

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[hokie66]

BA,
The brace you are describing is the transverse sway brace. The lateral bracing truss, tension only diagonals, is all in the plane of the top chord, and I thought the top chord was discontinuous at the joint, but the latest view which Doug attached shows a gusset there, so the "hinge" is just a half height connection.

 

[msquared48]

So then... could we all say that this is a 2.5 hinge arch and call it good?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[ToadJones]

I had the privilege a few short years ago to work on a train bridge demo/implosion job for a bridge built in the 1880's.
The bridge had a badly damaged portal frame at one end. We had to run some analysis for the demo guys.
Anyway....
You might be surprised by this...there was a total of 3 drawings for the bridge and, here is the kicker, the design calculations were included on one of the drawings.
Bridge stood, in service, for 100 years.

 

[bridgebuster]

Toad - I'm not surprised. I've worked on the rehab and replacement of quite a few bridges overe railroads. They were mostly trusses in the 100 to 200 foot range. I don't think I ever saw a set of plans with more than five sheets. Oddly enough, we were able to get the shop drawings from ConRail, butthat was back in the 70's and 80's. I tried without success a few years back. I guess with all the changing of hands with the railroad ownership the plans were all thrown out.

In NYC back in the late 19th/early 20th C. the railroads were responsible for constructing vehicular bridges if their trackage was to be installed on a city street.