FRP-confined steel-reinforced RAC short columns under eccentric compression: A parametric study and a new design calculation model

Recycled-aggregate-concrete (RAC) is mainly used in non-structural elements currently due to its inherent shortcomings from high water absorption rate and weak interfacial transition zones. To extend its structural use, RAC has been combined with FRP tube and steel section in this study to form a new type of composite element: the FRP-confined steel-reinforced concrete (FCSRC) column and the mechanical behavior of the short columns under eccentric compression was investigated. Specifically, the failure modes and stress status based on the strain distributions of the constituent materials of the FCSRC columns were discussed, and their ultimate load capacities were predicted. Test results revealed that the short FCSRC columns with RAC or natural-aggregate-concrete (NAC) exhibited very similar load-strain response except for the ultimate load capacity which was in direct proportion to filament winding angle and steel contribution ratio but inversely proportional to load eccentricity. Besides, the failure modes of the FRP tube were found related to the load eccentricity. The comparisons between test and predicted results indicated that the proposed design calculation model is capable to predict the ultimate load capacity of the FCSRC columns with either RAC or NAC under either concentric or eccentric loads.

Automated summary

This study investigates the mechanical behavior of recycled-aggregate-concrete (RAC) combined with FRP tube and steel section under eccentric compression. The failure modes, stress status, and ultimate load capacities of the composite elements are discussed and predicted.