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.• .. ,:� � •,/ � t..•"+ �• ;�ll+'•�}•`yam '.�,..`! �� y. - .•_. � . <br /> .y 1' oil <br /> W- -n. r , <br /> ve - VV/d - 204624/(14)(144)(1). - 102 psi (8) <br /> The ACI further states that the actual shear stress (ve) at the critical <br /> section shall not exceed 6 + flvc-, or 372 psig for deep beams with span/depth <br /> ratios less than L Vhen this limiting value is divided by, the owner <br /> required, 2 the limiting value is 186 psi. The actual calculated shear stress <br /> (we) of lot psi at the critical section is less than both the III psi maximum <br /> allowable shear stress (vc) and the 186 psi, critical section limiting shear <br /> stress. Therefore, the 14-ft long plug designed for the Friday Lowden <br /> pressure gradient requirement is adequate to meet the shear strength <br /> requirewent. <br /> Bending Strength Design- <br /> It is diffiwalt to obtain good adhesion between the concrete bulkhead and <br /> the roof and hoar of a tunnel. The difficulty lies is completely cleaning of <br /> �-. the floor and keeptag it clear of Mud and rock until the concrete is powVd <br /> Wj is completely filling all the voids in the roof. As a resit the analysis <br /> of beading ws based on a simply supported beam anchored at*the walls of the <br /> tuesel. This conservative design approach can be fw ther Justified by the <br /> - inability of obtainiag access to the upstream side of a bulkhead and the lag <br /> life expected of the plugs. . <br /> The first bwwding analysis performed is to calculate what length of <br /> wreinforced, plain, concrete bulkhead is necessary to beep the tensile <br /> beading stresses in the dawn stream face below ACI allowable stress. ACI <br /> (1977, sec 9.3.2) directs that a capacity reduction factor of 0.65 be cased in <br /> design. Further ACI (sec 15.11.1) directs that the design tensile bending <br /> strength be: t <br /> ft • 5 J (9) <br /> This wants to 273 psi for the 3,000 psi concrete to be used in the <br /> Friday Lowder Tunnel bulkhead. The owner required factor of safety reduces <br /> this design strength to 137 psi. MI also requires a 1.4 load factor for dead <br /> weight loads; such as bydraulic pressure.-- The required length of an.. <br /> unreinforced plain concrete bulkhead is.calculated as follows: <br />