TM 5-5420-278-100035 000035 00-23BRIDGE ANCHORAGE (Contd)LENGTHDEADMAN THICKNESSAfter calculating the required length of the deadman, check the thickness of thedeadman to ensure that the deadman will not break due to an insufficient length tothickness ratio. For timber:Dt must be less than or equal to 9.DfFor logs:DLmust be less than or equal to 5.diameterIf 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 morehorizontal).• Increase the thickness of the deadman by selecting a deadman with agreater thickness or by using two timbers, placed back to back.TOWER-TO-DEADMAN DISTANCEThe actual distance between the tower and the deadman can be described by the formula:C = H+DDslopewhere H is the actual tower height in feet, DD is the mean depth ofdeadman 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 Cis described as:Cmax = H + DDSince the maximum tower-to-deadman slope ratio is 1:4 (or 1/4), the maximumvalue for C is:Cmax = 4x(H + DD)Place the deadman at any distance from the tower, as long as that distance fallsbetween 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 fallsbetween the criteria given (1:1 and 1:4).RISE = 1 ft (0.3 m)SLOPE = RISE OVER RUN = 1:2 OR 1/2RUN = 2 ft (0.6 m)Figure 16. Estimation of Tower-to-Deadman Slope.
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