7. 27 This bending stress contribution·was added to the imposed tension stress and the stress versus thickness results were plotted. It was found that the hull thickness reached unreasonable levels due to the relative inefficiency of a simple plate supporting transverse load. It was then decided to let the minor stiffeners separating each lm x lm plate assume the role of absorbing a portion of the pressure load. This changed the nature of the problem to that of a square clamped plate stiffened by equally spaced beams in two orthogonal directions. In analyzing this problem, the Rayleigh-Ritz Method was employed with the Ritz Polynomial as the assumed deflection shape. Due to time constraints, two simplifications were used: a. The analysis involved only one assumed deflection mode. b. The stiffeners were of rectangular cross section, the width being equal to the thickness of the plate and the depth being four times the width. This analysis is presented in detail in Appendix VII.F. The resulting equation giving the applied stress level in terms of hull thickness for the failure mode is given below: - - 9.834xl06 5 1 2.2135xlo 22 a + 3.029xl0 -t + e 1 5.337xlo 15 t~ + 6.Sllxlo 17 tf Results for this relation are plotted on Figure 7.8 together with those for the normal loading condition. VII:4.4: Outer Hull: The analysis in this section proceeds in a manner similar to that of Section VII.4.2 with two exceptions. First, the loads to be sustained by the outer hull are different from those imposed upon the inner hull, namely: a. The atmospheric pressure load. b. The centrifugal load associated with the shield mass. c. The hull centrifugal load. d. The load associated with the remainder of the bulkhead mass.
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