Elastic buckling of FRP-strengthened cylinders with axisymmetric imperfections

Externally bonding of fibre reinforced polymer (FRP) composites has become a popular technique for retrofitting existing structures worldwide. Extensive research has been conducted in the last two decades on various topics such as strengthening concrete, masonry and timber structures as well as metallic structures. The vast majority of these studies have focussed on the failure strength, rather than on stability considerations. A study is currently being conducted at Edinburgh University on the strengthening of thin metal shell structures using FRP composites. This paper presents a numerical study of the buckling behaviour of FRP strengthened thin cylindrical shells with an axisymmetric imperfection. The results show that the buckling strength of the
shell under axial loading can be significantly increased by using only a small amount of FRP in the critical area of the imperfection. This outcome indicates that this technique is indeed very effective and economical for enhancing the buckling strength of thin shell structures, especially under conditions where a local defect causes the shell to fail the tolerance requirement.