Behaviour of CFRP strengthened CHS Members under Monotonic and Cyclic Loading

Tubular hollow members, though used in many civil and mechanical applications, are highly vulnerable structural elements when subjected to cyclic loading. They have been used extensively in both onshore and offshore civil infrastructure where cyclic loading can result from earthquake, waves, currents and wind. Thus, tubular hollow steel members may be required to undergo strengthening to withstand both static and cyclic loads. In the present study externally-bonded carbon fibre reinforced polymer (CFRP) has been used to strengthen the circular hollow section (CHS) steel specimens. A series of experiments on bare and CFRP strengthened CHS steel specimens subjected to monotonic and cyclic loading at the tip has been conducted to investigate the effect of CFRP strengthening technique on the structural behaviour of strengthened members under monotonic and cyclic loading. The results showed that the CFRP strengthening is effective to enhance the cyclic performance of CHS steel members by improving the moment capacity, moment degradation behaviour, secant stiffness, energy dissipation capacity and ductility compared to bare steel CHS members. In addition, the moment capacity of CHSs has been improved under monotonic loading due to the CFRP strengthening as well. Moreover, the impact of adhesive types on the structural response of the strengthened specimens was also investigated. This information will be helpful in the strengthening of CHSs for their intended applications