Abstract
The present study investigated the various failure modes of strengthened steel columns by mortar-filled fiber-reinforced polymer (FRP) tubes to analytically formulate the ultimate capacities of these steel columns. A simple and effective method, wherein a mortar-filled FRP tube was sleeved outside the steel member, was also formulated to enhance the buckling resistance capacity of compressed steel members. In addition, to facilitate the connection of the column to other structural members, the length of the sleeved mortar-filled FRP tubes is less than that of the original steel columns. Theoretical analyses were also performed on the critical sections of such composite columns at their ultimate states to identify their potential failure modes, such as FRP-tube splitting at the ends or on the insides of wrapped areas, local buckling at the steel ends of transition zones, and global buckling of the composite columns. The corresponding ultimate capacity of each failure mode was then analytically formulated to characterize the critical failure mode and ultimate load capacity of the columns. The current theoretical results were compared with those from literature to validate the applicability of the developed ultimate limit design approaches for FRP-mortar-steel composite columns.
Highlights
Shaat and Fam [9, 10] experimentally and theoretically examined compressed steel columns pasted with glass fiber-reinforced polymers (GFRP) composites and carbon fiberreinforced polymer (CFRP) composites, whose results indicated that Fiber-reinforced polymer (FRP) composites significantly strengthened the compressive steel members
E present study investigated possible experimental failure modes of strengthened steel columns by sleeved mortar-filled FRP tubes and developed a theoretical formulation to estimate the ultimate capacity of each presented failure mode, including FRP-tube end-splitting, local buckling at the steel end of the transition zone, and global buckling of the composite columns
A comparison between the theoretical formulation and experimental results was generated to verify the applicability of the presented formulations for composite columns and for the ultimate design of steel columns strengthened by sleeved mortar-filled FRP tubes
Summary
Compressive buckling is considered the most significant failure mode in steel columns due to its prevalence in many engineering accidents, such as the collapse of the Quebec Bridge in 1907 [1] and transmission towers in South China in 2008 [2]. ese events have prompted scholars and engineers to further investigate the buckling resistance capacity of compressed steel components to improve the design or repair of steel structures to effectively prevent compressive buckling and to improve buckling resistance capacity of its compressed members. The ultimate design approach was only developed and focused on the global buckling of composite columns, and the approach did not consider the failure modes of FRPtube end-splitting and local buckling at the transition zone ends of steel materials. E present study investigated possible experimental failure modes of strengthened steel columns by sleeved mortar-filled FRP tubes and developed a theoretical formulation to estimate the ultimate capacity of each presented failure mode, including FRP-tube end-splitting, local buckling at the steel end of the transition zone, and global buckling of the composite columns. A comparison between the theoretical formulation and experimental results was generated to verify the applicability of the presented formulations for composite columns and for the ultimate design of steel columns strengthened by sleeved mortar-filled FRP tubes
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