There are several methods of anchoring ribbon bridges. The anchorage system
used will depend on the following factors: stream velocity, length of bridge, time
available for bridge assembly, length of time bridge will be in place, and bank
conditions. Refer to Anchorage of Floating Bridges, in this work package, in
conjunction with the anchoring instructions listed below.
b. Short-Term Anchorage
Normally, the IRB is used as an assault bridge where it is necessary to
assemble, cross, and recover the bridge in a short period of time. A temporary
system of anchorage is required for this purpose. Short-term anchorage is a
temporary system of anchorage that utilizes BEBs and approach guys (cables) to
hold the bridge in place against the force of water current and vehicular traffic.
Positioning of the BEBs and installation of approach guys is accomplished
during bridge assembly whether by the successive bay method (WP 0033 00) or
swinging bridge method (WP 0034 00). Refer to Anchoring of Floating Bridges in
this work package in conjunction with the following instructions prior to
installation of short-term anchorage.
(1) Downstream deflection must be countered by the correct number of BEBs.
The spacing and correct number of BEBs needed to hold the bridge to its
centerline is based on water velocity and the number of individual bays in
the bridge assembly. Refer to table 1, and determine the number BEBs
required. In addition, the fuel consumption of the BEBs must be checked
every two hours, and at least two standby BEBs must be available when
refueling BEBs as necessary.
Stop bridge traffic while replacing boats, or damage to
equipment may result.
Note: If the bridge is to remain in place for long periods of time, an anchorage system
shall also be used.
Table 1. Bridge Erection Boats Required for Anchorage.
NUMBER OF BAYS PER MK I/II BEB
0.05.0 feet/sec (0.01.5 meters/sec)
5.08.0 feet/sec (1.52.4 meters/sec)
8.09.0 feet/sec (2.42.7 meters/sec)
9.010.0 feet/sec (2.73.0 meters/sec)
Anchorage system necessary