This structure is the largest and most complex on the railway. Spanning a deep gulch is the main span, length 13.87m, a box-section lattice truss carrying the main line rail track in both the upper and lower levels. A spiral on the north side on the gulch enables trains to cross over the lower level then the upper level in the opposite direction during its journey up the line.

From a study of the diagram, (right), the approach spans can be seen in relation to the main truss span, while to the right, an overall plan view of the structure is given.

Foundation data was largely destroyed in the fire of 18/1/95 but the builder could give reasonably precise details if required.

The main span is made of second hand steel sandblasted and 2-part epoxy resin sprayed. The structure was fabricated and partly assembled at the workshop, dismantled and re-assembled on site. 18mm galv. ms bolts were used throughout with a minimum of 2 bolts at each end of the members. Subsequently the entire span has been welded in the exception of reducing the reliance entirely on bolts.

The south end of the main span is supported on a steel trestle, founded on a pair of massive concrete feet cast in situ, and as with all foundations, pegged into the basement with driven heavy steel rail pegs.

Expansion joints are incorporate into the structure at both ends of the main span. Between hot summer and coldest winter an average movement of 5-6mm takes place. Systematic measurements of these movements were to begin mid 1996 and together with other regular tests will be incorporated into the bridge file.

For a copy of the full file of drawings, please email Ben Calcott, but be aware that it’s a 2MB zip file!