Railway Bridge TPG Flanges

[connect2]

So this particular railway bridge was built in 1928. The girder flanges are a pair of 6" x 8" x 3/4" (LLH) then with 3 - 5/8" x 18" cover plates. The top two plates are curtailed E.S. of the center line at the 15' and 20' marks. The bridge span is 56' -3". It' a ballasted, riveted TPG with closely spaced floor beams encased in a reinforced concrete diaphragm and knee braces, also encased in concrete, connecting the floor beams to the girder webs. We currently know nothing about the knee braces other than they are on the drawing on the one section through the bridge and appear to be angles. We will be opening at several locations to verify construction and condition. The bridge is skewed 38.4 degrees and a the track has a 4 degree curvature.

The oddity here is that the cover plate connected to the angles, the first cover plate, is two pieces terminating exactly at the center line of the span. So there is no continuous cover plate span. AREMA 1.7.2.1.c requires that at least one cover plate 'shall' extend the full length of the girder.
Any thoughts on these flanges, the butt splice, section properties.....
Thanks for the interest.

 

[bob33]

Maybe all they could get were 40 long plates and the designer did not trust butt welds in 1928. In which case plate 1 is a flange at the beam ends and a filler plate at mid-span. I would give the designer full marks.

 

[KootK]

bob's explanation rings true to me. Call it two cover plates:

1) one that only runs part of the span and;

2) another that is spliced, runs the full span, and elevates in the middle.

Naturally, the fastening has to reflect that scheme for it to be viable.