ARMY TM 5-5420-212-10-1
MARINE CORPS TM 08676A-10/1-1
When jacking down in this situation, always ensure the tilt of the jack leans inwards at 5% (1 in 20).This is best
achieved by adjusting the jack packing while the bridge is supported on packing and while the jack is being extended to a
new hood position.
h.
Jacking When Far Bank Has Crossfall
A slope of 5% (1 in 20) on the far bank can cause the side movement of a bridge. This is more obvious on:
(1)
Bridges longer than 2E + 12 bays.
(2)
When jacks are fully extended.
(3)
When jacks have their narrow side of base parallel to bankseat beam.
If the jacks are set with a tilt inwards [para. 4-19f.(5)] side thrust may be prevented. To prevent further side
movement, attach a puller cable to an anchorage.
4-21.
DAVITS
a.
General
Davits can be used as an alternative to jacks or crane to lift/lower end of bridge. It is recommended that davits are
used for bridges over 2E + 12 bays.
b.
Lowering Bridge
After final launch and the far bank has been lowered using the landing roller pedestal, the drill for lowering bridge
using davits is as follows. If counterweight has been added it will be necessary to clear the counterweight decks and curbs
at the end of bridge to enable the jacking brackets to be fitted, and allow room for a full stroke of the puller handles.
(1)
Unpin jacking bracket link from its stowed position and place on deck and over jack post bracket on
bankseat beam, ensuring to engage lugs of link on ramp ledge of bankseat beam.
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