FRP-Concrete-Steel Double-Skin Tubular Columns with UHPC/ECC: Concept and Compressive Behavior under Concentric Loading

This study presents the results of a comprehensive experimental program on the compressive behavior of hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (DSTCs) filled with ultrahigh-performance concrete (UHPC) or engineered cementitious composites (ECC). The use of UHPC or ECC, being a novel engineering material with unique characteristics, leads to many advantages of such hybrid DSTCs compared with conventional hybrid DSTCs with normal strength concrete (NSC). Particularly, the tendency of cracking of the FRP tube and NSC in conventional hybrid DSTCs could be reduced through the use of ECC with high tensile ductility and high tensile toughness, leading to excellent corrosion resistance. To understand the compressive behavior of DSTCs with UHPC or ECC, 12 DSTC specimens with different types of concretes (i.e., NSC, UHPC, and ECC) were prepared and tested, and the test results are presented in this paper. The test results demonstrated that DSTC specimens with UHPC or ECC could exhibit highly ductile behavior when a sufficiently large FRP confinement is provided, but the expected beneficial effects of fibers in UHPC or ECC are insignificant in the axial compressive behavior of DSTC specimens. Finally, the axial load resistances of different components of the test hybrid DSTC specimens were investigated, which demonstrated the beneficial effect of interaction of different components in the hybrid system, especially for DSTC-NSC and DSTC-ECC specimens.

Automated summary

This study presents the results of an experimental program on the compressive behavior of hybrid FRP-concrete-steel double-skin tubular columns filled with UHPC or ECC. The use of UHPC or ECC leads to advantages such as reduced cracking and excellent corrosion resistance compared to conventional NSC. Test results demonstrated highly ductile behavior of DSTC specimens with UHPC or ECC, but the expected beneficial effects of fibers in UHPC or ECC were insignificant in the axial compressive behavior of DSTC specimens. The axial load resistances of different components in the test hybrid DSTC specimens were investigated, showing the beneficial effect of interaction, especially for DSTC-NSC and DSTC-ECC specimens.