Ultimate strength of intact and dented steel stringer-stiffened cylinders under hydrostatic pressure

The aim of the study is to examine the effect of damages on the load carrying capacity of stringer-stiffened cylinders under external hydrostatic pressure. Experiments were conducted on three small-scale steel stringer-stiffened cylinder models that were fabricated by cold bending and arc welding. Drop tests with a knife-edge indenter were conducted on two test models to induce damage on the cylinders. Hydrostatic pressure tests of all models including an intact model were performed to characterize the ultimate strength behaviour of the stringer-stiffened cylinders in damaged and intact conditions. The results indicated that the effects of damage on the ultimate strength of stringer-stiffened cylinders were extremely low. Interestingly, during the collapse tests, it was also discovered that the shell failed several times after an initial failure, as evidenced by a sudden decrease in pressure. Subsequently, the shell recovered as “hardened-up” to reach a higher pressure level prior to the final collapse. Furthermore, the drop tests and hydrostatic pressure tests were simulated by using the finite element software package ABAQUS. The agreements between the tests and numerical predictions were satisfactory.