Posted By rpc7271 on 08/24/2008 3:36 PM
Guys, those "pieces" are called "spans" and it doesn't matter how many spans are in the bridge, it is one bridge, period. By the way, I design real bridges for a living working for an engineering consulting firm that designs highway and railroad bridges. The first bridge pictured is interesting. If no piers are added underneith it will end up being a "Single Span Steel Thru Truss Bridge" the second bridge shown is a "Three Span Steel Thru Truss Bridge" Marty's bridge is a "Three Span Steel Arch Bridge". Depending on how it is designed and works it could be a "Three Span Steel Arch Cantilever Bridge". The fourth & fifth bridges shown are one span of a multi-span bridge. That span is a Steel Thru Truss Span.
I am glad someone here has a working knowledge of the terminology. I would have said that Marty's bridge was a span and two half spans, but I can see that a span is a section of bridge between two supports, regardless of the distance or relative heights of the supports, being a span from one hillside to a pier, a span between the two piers and the third span being from the second pier to the second hillside.
But I wonder... is there a specific criteria to define a bridge "approach" as not a "span" of the bridge? Marty's bridge could (in my feeble brain) be construde as a single span from one pier to the other and the two outside portions being termed "approaches".
I guess it could be based on whatever the archetech/engineer decided to call the various portions, or who got the contract to build the various portions.
