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. . w .•� �. � 1« fir- ',�:,. � . �` <br /> C - T 0.85(f'c)ba - Asfy 0.85(3000)12a - 60000AS <br /> a - Asf//0.8S(f'c)b - 60000As/0.85(3000)12 - 1.96078As - <br /> Sumation of moments about center of compressive stress area using equation <br /> (18). note: rebar embedment is 3 in. (0.2S ft) <br /> i <br /> He - Asfy(d - a/2) (18) <br /> d . depth from top of beam to center of reinforcing steel (is.) <br /> Me - Nominal moment capacity (in:lb) <br /> • t d - a/2j - I(14 - 0.25)12 - 1.9078AS/21 <br /> � As r( � 2 ft-lb <br /> Ne - 6000WA (16S - 0.98039AS) - 9900000AS.- S8824As <br /> the design moment is also: <br /> Solution for reinforcing steel area: <br /> 730800(12)/0.90 - 9900000AS - S8824Ast <br /> SWMi2 - A9900000AS • 9744000 - • <br /> Therefore, the required As - 00990 sq in./ft of beam. <br /> Rebar specification, to resist the maximum bending moment, is #8 bars on <br /> 948. spacing which provides 1.05 sq ia. of steel per foot of beam which will <br /> supply a 861,000 ft lb bending moment 'resistance. The design bulkhead <br /> thickness typically required to prevent leakage due to the pressrre gradient <br /> and to resist shear forces makes the use of a simple beam design for bending <br /> • extremely conservative. The bending deformations causing appreciable <br /> reinforcing steel strain. and therefore tensile stress, will not be linear due <br /> to the bulkhead. thickness and the lateral restraint provided by the tunnel <br /> ribs. Bulkhead failure world most likely occur by concrete yielding of a <br /> pressure arch that would develop in the upstream side,, rather than as the <br /> -12- ' <br />