heavier loads, have longer service lives, and dissimilar maintenance constraints
compared to their highway counterparts, other factors, including fatigue and
maintenance issues, tend to influence railway structure design more than roadway
structures.
Once the designer has established the first pass at the load environment for the subject
structure, the primary difference between a highway structure and a railway structure
should become obvious. In the typical railway structure, the live load dominates all of
the other design considerations. For the engineer accustomed to highway bridge
design, where the dead load of the structure itself tends to drive the design
considerations, this marks a substantial divergence from the norm. Specifically, the
unacceptability of high deflections in railway structures, maintenance concerns and
fatigue considerations render many aspects of bridge design common to the highway
industry unacceptable in the railway environment. Chief among these are welded
connections and continuous spans