ARMY TM 5-5420-212-10-1
MARINE CORPS TM 08676A-1 0/1-1
c.
Bridge length
Read and note the number of bays and bridge length, Table 3-15 columns (c) and (d).
d.
R Distance
Read and note the R Distance, Table 3-15 column (e).
e.
Nose configuration
Read and note the nose configuration, Table 3-15 column (f).
f.
Key construction points
Identify, locate, and take elevations at the key construction points. These constructions points are explained
below and shown in Figure 3-10.
(1)
F Peg-Designates the location of the far bank end of bridge (outer edge of bankseat beam). Initially
placed 0.6 m (minimum acceptable) from the A peg on the far bank. This 0.6 m, between the A and F pegs is the amount
of bridge that will bear on the far bank, and is known as the far bank bearing.
(2)
A Peg-Edge of firm ground on the far bank.
(3)
AR Gap-The distance measured between the A and A’ pegs. This is the actual gap to be spanned by
your bridge.
(4)
A’ Peg-Edge of firm ground on the near bank.
(5)
F’ Peg-Designates the location of the near bank end of bridge (outer edge of bankseat beam). The
distance (determined later),from the A’ to F’ peg is the amount of bridge that will bear on the near bank, known as near
bank bearing. The minimum acceptable near bank bearing is 1.4 m.
(6)
FRB Peg-Designates the position of the front roller beam (FRB). The distance from the A’ peg to the
center of the FRB can not be less than 0.9 m, and from the FRB to the F’ peg can not be less than 0.5 m. The placement
of the FRB is determined by using the length of bridge (L), AR Gap, far bank bearing, and bridge overhang (0.5 m) to
obtain an X distance (from A’ to FRB). Placement of the FRB in this manner will ensure minimum effort during the jack
down operation.
(7)
RRB Peg-Designates the location of the rear roller beam (RRB). It is placed 4.6 m from the FRB
(measured center to center).
(8)
O Peg-Marks the clear distance behind the front roller beam required to construct the bridge. It is
positioned by measuring the R distance, Table 3-15, column (f), behind the FRB peg.
g.
Calculate bearing
The minimum and maximum bearings for all DS bridges are shown in the Table 3-16 and Figure 3-10. To calculate the
actual locations of the F and F’ pegs, the following procedure is used:
Near bank bearing = bridge length (L) - (AR Gap + 0.6 m)
Where:
Bridge length is obtained from column (d) of Table 3-15.
The AR Gap was measured in the first step of the design procedure.
An assumption of 0.6 m is made at this point in the calculation sequence be cause this is
in the minimum acceptable bearing allowed on the far bank.
TABLE 3-16. Bearings DS 1-12 Bay
Bearings
Near bank
Far bank
Minimum
1.4 m
0.6 m
Maximum
2.3 m
2.3 m
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