Behavior of FRP-Steel Confined Concrete Tubular Columns Made of Expansive Self-Consolidating Concrete under Axial Compression

Abstract

A total of 32 fiber-reinforced polymer (FRP) confined concrete columns are manufactured and tested under axial compression including 8 FRP-confined solid columns (FCSCs), 4 FRP-confined concrete-filled steel tube columns (CCFTs), and 20 hybrid FRP-concrete-steel double-skin tubular columns (DSTCs). Key parameters include FRP layers, diameter of steel tube, and presence or absence of an expansive agent and concrete filling for the steel tube. Due to the effect of the expansive agent, prestress in concrete is detected in all specimens with expansive self-consolidating concrete (ESCC). For FCSCs and CCFTs, the normalized intercept, inflection and ultimate load for ESCC specimens are higher than those of self-consolidating concrete (SCC) specimens. For DSTCs, when the inner steel tube is filled with concrete only normalized ultimate loads are improved by in ESCC specimens compared with SCC specimens. For hollow DSTCs, however, an expansive agent does not improve the axial behavior. The number of layers of FRP show a positive influence on the normalized intercept, inflection, and ultimate load of ESCC FCSC specimens. In addition, test results for hollow DSTCs indicate that normalized ultimate loads decrease with the increase of steel tube diameter. An existing model used to predict the compressive strength and ultimate axial strain of FCSCs shows good agreement.