Eccentric compressive behavior of novel concrete-filled FRP tubes integrated with gridded rib layer and multi-angle winding layer

Abstract

Novel Concrete-Filled FRP Tube (CFFT) columns integrated with Gridded Rib layer and multi-angle winding layer (referred to as GR-CFFT columns) are proposed to improve the bending performance of normal CFFT columns. The FRP tube of GR-CFFT columns consists of gridded rib layer and multi-angle winding layer which are integrated together with continuous fiber winding. The eccentric compressive behaviors of three GR-CFFT columns under different load eccentricities were investigated experimentally and compared with three corresponding normal CFFT (N-CFFT) columns. Failure modes, load-lateral deformation curves and development of axial strain and hoop strain of GR-CFFT columns were presented and discussed considering variation in eccentricity. The test results confirm the effectiveness of the proposed GR-CFFT columns. The end slip between concrete and FRP tube of GR-CFFT columns was reduced by over 74.5% compared with that of N-CFFT columns. The ultimate bearing capacity was increased by 46.3%, 81.7%, and 96.9% respectively when the eccentricity was 20 mm, 60 mm, and 80 mm compared to that of N-CFFT columns. Meanwhile, theoretical sectional analysis model using strip method for load-strain curves of GR-CFFT columns was established and validated with experimental results. In this model, constitutive relationship of concrete under non-uniform confinement was adopted, and the discrete gridded rib layer was equivalent to a homogeneous continuous winding layer for simplification. The model was further used in parameter analysis, and the influences of thickness and combination of winding angles of multi-angle winding layer, existence or absence of gridded rib layer and variation of concrete strength were investigated.