Experimental study on FRP strengthened steel tubular members under lateral impact

The hollow structural members are highly vulnerable structural components subjected to transverse impact loads. These tubular members have been used widely in both onshore and offshore structures where lateral impact force can be expected from moving vehicles/vessels or terrorist attacks. Thus, strengthening of steel hollow tubular members is required to safely carry both service static and imposed dynamic impact loads. This paper presents the results from a series of tests on bare and fibre reinforced polymer (FRP) strengthened circular hollow section (CHS) steel members subjected to transverse impact loading at mid span. A total of fourteen (two bare and twelve strengthened) medium scale specimens were tested to investigate the effect of FRP wrapping on the global and local deformation capacity of strengthened members under drop hammer impact. Both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) sheets were used as strengthening materials. The results indicate that the FRP strengthening of the tubes enhances their impact resistance capacity by reducing lateral displacements up to 29% compared to bare steel CHS specimen. The influence of FRP type, CFRP orientation, CFRP thickness and effective bond length on the structural response and failure behaviour of wrapped members were investigated. The results showed that the application of FRP in the longitudinal direction was effective to control the global deformations whereas the hoop layers were effective in reducing local inward deformations of CHS members.