An experimental study on externally pressurized stiffened and thickened cylindrical shells

• Fully stiffened specimens were more stable relative to the partially stiffened ones.
• A new collapse mode was seen for the fully stiffened specimens.
• For thickened specimens the increase in the capacity was noticeable.
• Installation of the thickening is convenient so it is preferable for some applications.
• The thickening resulted in only slightly less capacity compared with the stiffening.

It has long been identified that stiffening of steel shells is one of the most effective ways of enhancing the capacity of these structures. Stiffeners largely in the form of welded elements have been employed to strengthen shell structures in which the stiffeners generally cover the whole length of the structure. In this research the effect of partial and full length stiffening of shells was studied in which the stiffeners were attached without welding to avoid the adverse effect of the residual stresses. Furthermore, local thickening of the shells by the same stiffening strips was investigated and the results were evaluated against the plain specimen. The effect of strengthening provided by local thickening was slightly less but comparable to that provided by the stiffeners.