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. Due to service loads increment, errors in design, effect of severe environments or loss of material properties, tubular hollow steel members may require to undergo strengthening to withstand both static and cyclic loads. In the present study, a series of experiments on bare and externally-bonded carbon fibre reinforced polymer (CFRP) strengthened CHS steel members subjected to monotonic and cyclic loading has been conducted to investigate the effect of CFRP strengthening technique on the structural behaviour of strengthened members. 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 CHS members 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.