Regarding the concrete trestles near Chillicothe, the alignment chart
shows 5 concrete pile trestle (CPT) bridges in 3 miles across the
Grand River valley. They were as follows: Bridge 131.42 - 21 spans,
Bridge 131.79 - 52 spans, Bridge 132.20 - 46 spans, Bridge 133.30 -
14 spans CPT (plus 3 Deck Plate Girders and 3 - 148' Thru Trusses),
and Bridge 134.06 - 24 spans.
As I recall, the span length on these bridges was 16'. This length,
along with 20' and 25', were standard span lengths used by CB&Q.
Each span actually consisted of two slabs, each 7 ft. wide. The
thickness of the slab was 36" at centerline of track, and 42" at the
curb. The curb was 6" wide at the top, sloping to about 10" wide at
the bottom of the curb. Top of tie is shown on plans at 6" above the
top of the curb, as most of the concrete trestles had a timber
ballast stop attached to the top of the curb. Each slab had "half"
drain holes placed at 4'-6" centers at centerline of track to allow
moisture to drip out. The tops of the slabs were treated with car
cement for waterproofing.
CB&Q B&B forces built many of these slabs in specific locations, and
then shipped them to bridge sites for placement. Each slab had two
lifting stirrups made out of 2" diameter rod. The stirrups were
placed about 2'-3" in from each end, and slightly off-center toward
the curb side, so that the spans could be lifted level.
These concrete spans were heavily reinforced and were almost
indestructable. Many of the spans still around today show cracks at
the piers, and reinforcing bars showing on the underneath side, and
yet are still carrying trains. And many spans support considerably
more ballast than what they were designed for. I have read ( I can't
remember where) that CB&Q loaded some concrete spans to failure
(cracking), and then installed them and ran a 2-10-2 locomotive over
them, and they barely deflected.
The plans I have for the 20' and 25' spans are dated 1911, and the
CB&Q built them until at least the mid-50's. By that time CB&Q was
experimenting with pre-stressed concrete slabs which were shallower
(a 20' span was only 18" deep). In 1954, CB&Q installed the first
pre-stressed concrete span in a railway bridge in the United States
in Bridge 38.64 at Hunnewell, MO.
Glen Haug
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