no such simple solution can be hoped for in the case of the cylinder stiffened by elastic rings. 

 The reason for this is that the deformation mechanism is one in which the transverse displace- 

 ments are radially outward in the region of the major axis and radially inward in the region of 

 the minor axis with respect to the initial undeformed cross section. The elastic-ring analysis 

 indicates such behavior, and it is the development of extreme circumferential bending varying 

 around the periphery which precludes the use of the equivalent cylinder with local radius of 

 curvature concept to predict the deformations and stresses. This is contrary to the cases of 

 the simply supported and clamped oval shells of very short length analysed at Brooklyn Poly- 

 technic Institute in which the transverse displacements are all radially inward around the 

 periphery of the oval cross section. 



The analytical results indicate that whereas the area of the stiffening rings plays the 

 dominant role in the shell deformations of a stiffened circular cylinder, the inertia of the ring 

 cross section is of paramount importance in the deformation of a stiffened oval cylinder. This 

 is due to the fact that the axi symmetric nature of the circular cylinder problem precludes the 

 development of tangential (v) displacements whereas the tangential displacements are very 

 important in the oval cylinder problem. These displacements arise as a consequence of a 

 shear flow which develops along the oval periphery to maintain overall equilibrium of the 

 forces. Due to symmetry considerations, this "running shear" is zero at the two extremes of 

 each of the major and minor axes of the oval cross section. This brings up an important 

 problem with regard to the location of the stiffening rings, i.e., whether they are located on 

 the outside or on the inside surface of the noncircular shell will determine the nature of the 

 bending moments caused by the shear flow and the fact that the shell and frame median lines 

 are not truly coincident. This "eccentricity" between the shell and frame median lines will 

 determine the magnitude and sense of the circumferential bending moments and their effect on 

 further distortion of the noncircular shape. 



To assist in checking out the analysis developed by the Polytechnic group, the Model 

 Basin provided data^ obtained from the initial test of the model presented in this report. 

 Comparison of the theory and Model Basin tests, reported by the Polytechnic group, is given 

 in Reference 8. 



Many of the figures shown in this report have been taken from Reference 8. 



DESCRIPTION OF MODELS 



Model EC-1 is an internally stiffened cylinder with a quasi-elliptical cross section. 

 Two radii were used to develop the oval cross section of the model as shown in Figure 1. 

 The shell of the model was fabricated in four strakes of HY-100 steel plating with the dia- 

 metrical strakes having the same thickness and radius. The yield strength of the thicker 

 shell plating was 96,000 psi and that of the thinner shell plating was 102,000 psi. The model 

 was stiffened with transverse T-frames also fabricated from HY-100 steel plating. Heavier 

 frames were placed at the two ends of the model to preclude premature failure near the rigid 

 closure bulkheads. 



