Collapse of externally pressurized elliptical steel cylinders stiffened with helical composite stripes

This study investigates the collapse of externally pressurized elliptical steel cylinders stiffened with four helically wound composite stripes. The cylinders have a length of 320 mm, a major axis of 80.5 mm, and a major-to-minor axis ratio of 1.002. The width and warping angle of the composite stripes are 58 mm and 55°, respectively. Elliptical steel cylinders without stiffening stripes are also considered. Three nominally identical elliptical steel cylinders and three nominally identical elliptical steel–composite cylinders are designed, fabricated, geometrically measured, and hydrostatically experimented. Linear eigenvalue and nonlinear RIKS analyses are performed to evaluate the collapse properties of the fabricated samples. The experimental and numerical data agree favorably. The results indicate that the reinforcement provided by the composite stripes approximately doubles the loading capacity of the steel cylinders. Furthermore, elliptical steel–composite cylinders are found to be less sensitive to imperfections than are steel-only and circular steel–composite cylinders.