[urbancog]

Looking at the bridge abutment configuration and the assembly photos, they may be building 4 separate bridge decks - two for Lower Jarvis, two for Lower Sherbourne. With each track sitting on ballast on a steel tray mounted on the cross beams, all supported by an I beam at each side.

Using MS-Word as a sketch tool:

 

[smallspy]

Looking at the bridge abutment configuration and the assembly photos, they may be building 4 separate bridge decks - two for Lower Jarvis, two for Lower Sherbourne. With each track sitting on ballast on a steel tray mounted on the cross beams, all supported by an I beam at each side.

Using MS-Word as a sketch tool:
View attachment 678541

That is absolutely a way that a bridge can be built. But that's not how these ones will be built.

The beams that have been delivered are too short to be used alongside the tracks. If you look, the bracing that will tie the beams together is the same height as the web of the beam. These beams will be used underneath the tracks, and will have a structure built overtop of them to support the ballast, and then the track on that.

Dan

 

[urbancog]

What led me to speculate (and it's pure speculation, I've not seen any drawings) that the track will sit between the beams is this detail, where the cross beams are sitting on the bottom flange of the main I-beam:

Coupled with the odd notched design of the abutment:

These prefabbed trough units may be designed to sit between the angled supports on the cross beams:

 

[mburrrrr]

One set partially assembled with bottom braces. Interesting angle joints for the next layer.

 

[mburrrrr]

Lower Sherbourne

Ground wires.

Lower Jarvis