(2) Anchor Wale . 



Maximum moment over support = 



wa/ 

 3 



For a 12- by 10-foot wale with 2-inch witith squared deducted for tie 

 rod hole: 



Bending stress = ^'^?"/ ^^ = 600 psi 



143 



maximum moment at span = ~ j = 1,600 x |- - 7,200 = 5,600; 



9 ■? 

 section modulus (no hole) = 11.5 x, -^= 173 cijbic 



inches ; 



bending stress = ^^^OO^x 12 ^ ^^^ ^^^^ 



h. Passive Resistance Anchorage . The anchorage for the bulkhead 

 (Figure 3) relies on passive resistance. To locate this anchorage at 

 a safe distance behind the bulkhead, a slope line is drawn from the 

 bottom of the sheet piles to the finished grade at an angle to the 

 horizontal, where is the angle of internal friction of the material. 

 For the sand backfill assumed, is taken as 30°. The upper edge of 

 the anchorage should be located beneath or outside this slope line. 



For a continuous anchorage (Figure 2) in which the height of bear- 

 ing contact is only 1 foot, with center of bearing contact located 5.5 

 feet below the ground surface, the ultimate resistance is approximately 

 equal to the bearing capacity of a continuous strip footing of a 1-foot 

 width located at a depth of 5.5 feet (Terzaghi, 1943), The overburden 

 pressure is 5.5 feet x 100 pounds per cubic foot which is 550 psf. 

 Then by Terzaghi (1943) :. 



Ultimate resistance = 550 N' where N' is a bearing capacity factor to 



q q 



be taken from curve. N' is read as 7.0. 



q 



Ultimate resistance = 550 x 7.0 = 3,850 psf. 



For a 7-foot length of anchor wale to each tie rod, the ultimate 

 resistance of the anchor wale is 7 x 1 x 3,850 = 26,950 pounds per tie 

 rodo With a tie rod reaction of 1,600 pounds per foot, x 8 feet = 

 12,800 pounds, the factor of safety is iLQSO ^ 2.1. The resistance 



12 , 800 

 of the anchor post would increase this safety factor somewhat. A value 

 of 2 is considered adequate. If an arbitrary limit of 3,000 pounds per 

 square foot (1.5 tons) is assumed for the ultimate resistance (Figure 

 5), the total resistance including the anchor post will still provide 

 a safety factor of 2. 



25 



