Talk:Bollman Truss Railroad Bridge

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[edit] Article name

I found several variations for the name of this bridge. I ended up using the one in the National Historic Landmark program -- "Bollman Truss Railroad Bridge". I made redirects of the others. — Eoghanacht ^talk 02:50, 1 April 2006 (UTC)

[edit] Suspension bridge

Occasionally this bridge is referenced as being a suspension bridge as well as a truss, but not consistently. The bridge is always refered to as a truss, however. It has been too long since I took my static structures classes to confirm if it should be classified as just a truss or a combination suspension system. So I just removed the reference to the suspension bridge from the main article as being unverified. — Eoghanacht ^talk 14:27, 4 April 2006 (UTC)

It's definitely a truss bridge, though this is not as obvious for the deck version. The key is the presence of the compression members; it's composed of the same sort of force triangles as other truss systems, and the through version clearly relies on the upper chord of the bridge to keep the pylons apart. A true suspension bridge relies on symmetry of forces to eliminate the tortional forces on the pylons.

Bollman's patent drawing is a bit confusing because it doesn't show any members across the bottom. If I recall correctly, actual examples did include those members (providing stiffening). In any case the compressional elements of the deck are crucial in the deck version. Mangoe 18:05, 30 June 2006 (UTC)