ARMY TM 5-5420-212-10-1
MARINE CORPS TM 08676A-10/1-1
At this point, decide whether the first AR Gap range found provides the best bridge for the expected
mission, or if you will have to go to the next higher AR Gap range and bridge.
1. AR Gap measured = 5.7m
MLC required = 70
2. Select Bridge. First AR Gap range that brackets 5.7m is in Section (a), Single Story 4-12 Bays. The range is
3.7 - 7. 1m, 4 bay bridge with MLC 70. The next range also brackets 5 7m, 5.6 - 9.0m, 5 bay bridge with MLC 70.
At this point, look at the soil bearing capacity, traffic loads, and weather. If the soil bearing capacity is low
and large numbers of heavy vehicles are to cross during Inclement (rainy) weather, it would be wise to build the 5 bay
bridge. The 5 bay would have more bridge bearing on the ground (on each bank) than the 4 bay.
If the soil bearing capacity is high, and the vehicle traffic is expected to be light and weather fair the 4 bay
bridge might be suitable, it would conserve resources. The 4 bay would have less bridge bearing on the ground (on each
bank) than the 5 bay.
3. Once the AR Gap Range has been determined, proceed to the appropriate paragraph.
paragraph 3-12, 4-72 Bay SS Design.
paragraph 3-13, 9-12 Bay SS Design on restricted site
paragraph 3-14, 2E+1 - 2E + 12 Bay DS Design
paragraph 3-15, 2E+1 - 2E+12 Bay DS Design on restricted site
paragraph 3-16, 2E+13 - 2E+22 Bay DS (w/oLRS) Design.
paragraph 3-17, 2E+13 - 2E+22 Bay DS (w/LRS) Design.
3-11 DESIGN PHASE 2.
In this phase, the information obtained in phase 1 is used to determine the height setting of the roller beams and the
position of the launching nose cross girder. This phase is usually done in a rear area, away from the site.
SINGLE STORY 4 thru 12 BAY DESIGN
The procedures that follow are for design of SS 4 through 12 bay MGBs on normal sites only:
Measure the AR Gap (para. 3-10a)
Select a bridge (para. 3-10b and Table 3-7 and 3-8)