Braced vertical sheeting is used to brace a deep open-trench excavation made for the purpose of installing a large-diameter water main (pipe) for a municipal supply system. The excavation will be 20...

Braced vertical sheeting is used to brace a deep open-trench excavation made for the purpose of installing a large-diameter water main (pipe) for a municipal supply system. The excavation will be 20 ft deep, extending through sandy soils (unit weight of 120 pcf). The sheeting will be supported by three rows of struts. The top strut will be level with the ground surface, the second strut 7 ft down, and the third strut 14 ft down from the ground surface. In plan view, the struts are positioned 12 ft apart. Calculate the force in each strut (ref. Figures 44, 45, and 46).