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Memo to Tom Schreiner 5 February 21, 2006 <br />Bulkhead Cost Estimate Permit No. M-1983-141 <br />Desien for Plain Concrete Deep Beam Bending Stress, Main Bulkhead <br />The Applicant has proposed that plain concrete (unreinforced) bulkheads be constructed. American <br />Concrete Institute codes can be used to determine the required length for a plain concrete bulkhead to resist <br />deep-beam bending stress. For the analysis, the dead or fluid load acting on the bulkhead is multiplied by <br />1.4 (ACI 318-89, Section 9.2.1) and the plain concrete bending strength reduction factor of 0.65 is applied <br />(ACI 318-77, Section 9.3.2). ACI directs that the design tensile bending strength be: <br />f, = 5 f ~ (ACI 318-77, Section 15.11.1) <br />f, = 5 3000 = 273 psi, assuming that minimum 3000 psi compressive strength is specified <br />w =1.4 x p x 144in Z / ft2 =1.4 x 265 x 144 = 53424 pounds per foot <br />Mu _ w 82Z _ 53428 x 8Z = 427392 foot pounds <br />M _ M„ _ 427392 = 657526 foot pounds <br />" 0.65 0.65 <br />I bh'l12 <br />S=-= <br />c h/2 <br />_ Mn _ M~ _ 6xM~ <br />f S (bh'l12)l(h/Z} bh2 <br />hZ _ 6xM~ _ <br />bx f <br />6 x 657526 <br />1 x 273 x 144in2 / ft2 <br />=100 square feet <br />h =10 feet <br />where: f =flexural stress (psi) <br />f'~ =concrete compressive strength (psi) <br />w =pressure (dead) load (pounds per foot) <br />p =pressure head (psi) <br />M„ =maximum bending moment (foot pounds) <br />k = adit width (feet) <br />M„ =design bending moment (foot pounds) <br />S =section modulus (cubic inches) <br />I=moment of inertia (inches°) <br />c = centroidal distance (inches) <br />