Behaviour of CFRP strengthened CHS members under monotonic and cyclic loading

Abstract

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, Please cite this articla as, "Tafsirojjaman T, Fawzia S, Thambiratnam D, Zhao XL. Behaviour of CFRP strengthened CHS members under monotonic and cyclic loading. Compos Struct 2019;220:592-601." 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.

Structural behaviour of CFRP strengthened beam-column connections under monotonic and cyclic loading

“…The local buckling behaviour of steel members was effectively delayed by retrofitting with FRP laminates [25]. The efficiency of the CFRP strengthening method subjected to cyclic loading has been confirmed by enhanced moment capacity, stiffness, ductility, energy absorption and delayed local buckling of structural members [23,26]. The fatigue behaviour of the steel plates [28,29] and steel members [30] have been improved by strengthening with FRP.…”

“…Overstrength and ductility also improved significantly in the FRP strengthened frames compared to their bare counterparts [20]. Recently there has been researched into retrofitting existing steel members with FRP to overcome strength deficiencies [21][22][23][24][25][26] and results have confirmed the benefits of FRP to repair or strengthen steel members. CFRP strengthened the circular hollow section (CHS) showed a higher load capacity compared to the bare section under pure bending [21] and four-point loading [22].…”

“…CFRP strengthened the circular hollow section (CHS) showed a higher load capacity compared to the bare section under pure bending [21] and four-point loading [22]. The moment capacity of cantilever circular hollow members under monotonic loading was also enhanced by CFRP strengthening [23]. Kabir et al studied the durability of CHS members wrapped with CFRP under cold weather [24] and seawater [27] and confirmed the efficiency of CFRP wrapping.…”

Performance of FRP strengthened full-scale simply-supported circular hollow steel members under monotonic and large-displacement cyclic loading

“…Hence, a proper insulation system is an important matter that needs to be explored through significant research work, to enable a suitable option to protect FRP strengthened members under expected fire during a seismic event. CFRP strengthened CHS has been shown to have improved structural performance such as higher stiffness [15], greater load capacity [16], greater ultimate bending strength [17], higher ductility [17], delayed local bucking [18] and energy dissipation capacity [17,19] compared to its bare counterpart. This improvement of structural performance was found to increase as the number of CFRP sheets increased [15,19].…”

Experimental Investigation on the Buckling Capacity of Angle Steel Strengthened at Both Legs Using VaRTM-Processed Unbonded CFRP Laminates

“…Indeed, the externally bonded strengthening technique is effective for enhancing the performance of steel structures. It has been convincingly proven that this technique is able to increase: the compression capacity of short steel members [ 11 , 12 , 13 ], flexural capacity of steel beams [ 14 , 15 , 16 , 17 , 18 ], torsional capacity of steel members [ 19 , 20 ], load bearing capacity of steel shear wall [ 21 , 22 , 23 ], tensile capacity of steel plates [ 24 , 25 , 26 , 27 , 28 ], and also buckling capacity of long steel columns [ 29 , 30 , 31 ]. However, this strengthening technique is considered to have drawbacks.…”