TM 5-5420-278-10
0035 00
0035 00-23
BRIDGE ANCHORAGE (Contd)
LENGTH
DEADMAN THICKNESS
After calculating the required length of the deadman, check the thickness of the
deadman to ensure that the deadman will not break due to an insufficient length to
thickness ratio.
For timber:
Dt must be less than or equal to 9.
Df
For logs:
DL must be less than or equal to 5.
diameter
If the length to thickness ratio is exceeded, decrease the length requirements.
This can be accomplished by one of the following methods:
• Increase the mean depth of deadman (DD).
• Increase the tower-to-deadman slope ratio (the cable should become more
horizontal).
• Increase the thickness of the deadman by selecting a deadman with a
greater thickness or by using two timbers, placed back to back.
TOWER-TO-DEADMAN DISTANCE
The actual distance between the tower and the deadman can be described by the formula:
C = H + DD
slope
where H is the actual tower height in feet, DD is the mean depth of
deadman in feet, and the slope refers to the tower-to-deadman slope ratio.
Given that the minimum tower-to-deadman slope is 1:1, the minimum value for C
is described as:
Cmax = H + DD
Since the maximum tower-to-deadman slope ratio is 1:4 (or 1/4), the maximum
value for C is:
Cmax = 4x(H + DD)
Place the deadman at any distance from the tower, as long as that distance falls
between these minimum and maximum values. Once the deadman is positioned,
make a check of the tower-to-deadman slope to ensure that the actual slope falls
between the criteria given (1:1 and 1:4).
RISE = 1 ft (0.3 m)
SLOPE = RISE OVER RUN
= 1:2 OR 1/2
RUN = 2 ft (0.6 m)
Figure 16. Estimation of Tower-to-Deadman Slope.
