Section VI. ANCHORING THE BRIDGE AND DEFILE MARKERS
The requirement for anchorage will be determined during site reconnaissance. Factors
such as slope of finished bridge, volume and type of traffic, and bank conditions will be
used to determine if anchorage is required.
of Finished Bridge
The steeper the slope of the finished bridge the greater the possibility that anchorage is
needed. Consider crossfall of bridge along with longitudinal slope. Do not consider the
above to mean that completely level bridges will not need anchoring, as the volume and
type of traffic and bank conditions must also be considered. Bridges constructed on solid
banks or on packing may creep under a high volume of traffic (especially armored,
tracked vehicles). If anchorage is not installed, a bridge should be checked during
crossing of traffic for any sign of creeping. If creeping is detected, anchorage should be
3.15.3 Volume and Type
Heavy wheeled and tracked vehicles may cause the bridge to creep. This is the result of
impact loads against the end of bridge, and braking/accelerating on the bridge. Control of
vehicle approach speed and movement across the bridge will reduce these loads. High
volume of medium to heavy vehicles in one direction may cause creeping. Vehicles may
be stopped prior to impact on the end of bridge and drivers instructed to maintain a
constant safe speed, not to shift gears and not to make any sudden stops.
Bank conditions that will allow slow settling of the end of bridge will tend to reduce the
amount of creeping. Firm, solid banks will increase the need for anchorage.
After considering the basic factors, the final determination if anchorage is needed will be
made by the bridge commander. If anchorage is not installed, the bridge must be checked
regularly for any sign of creeping. If detected, the severity of creeping will be determined,
and anchorage will be installed if deemed necessary.
A DSB anchor consists of an anchorage beam, anchor earth holdfast (AEH) and anchor
earth holdfast pins (AEH pins).
For soil with bearing capabilities of 1.86 ton/ft2 (18162.6 kg/m2), the standard anchor
configuration is shown in Figure 3. 78. For soil with a bearing capability between 1.86
ton/ft2 (18162.6 kg/m2) and 1.00 ton/ft2 (9764.9 kg/m2), use the anchorage configuration
shown in Figure 3. 79. For soil bearing capability of 1.00 ton/ft2 (9764.9 kg/m2) and less,
use a dead weight.