I believe you will find the 1/8" per 10' applies to camber and sweep. Overall length is a different story, the steel has to hit it's support points. With 450' span, I would hope there was some adjustment somewhere. I'd say whatever your total tolerance from each of the bearing points, divided by the number of elements in the span, would be your tolerance on the overall length of each element.
CHGuilford
You`ll find a great deal of material on the `Code of Standard Practice of Steel Buildings and Bridges`, published by the American Institute of Steel Construction, which you can download for free at www.aisc.org
Giovanni S. Crisi
Sao Paulo - Brazil