Strain localization analysis using digital image correlation for PVA fiber-reinforced concrete-filled FRP tubes under compressive loading

This study presents the outcomes of the first experimental study on the strain localization of polyvinyl alcohol (PVA) fiber-reinforced concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs). 24 CFFT specimens were prepared and tested with various instrumentations, such as linear variable differential transformer (LVDT) and strain gauges (SGs), to record required full-field strains, i.e., axial, lateral and Von Mises strains. The strain evolutions over the surface of the specimens were recorded during axial compression loading. The FRPs were prepared with carbon, S-glass or basalt fiber to examine the influence of the fiber type and confinement stiffness on the behavior and strain localization of CFFTs. The evolution of Von Mises strains was determined and studied under axial compression. The obtained results show that although the general pattern of localization for both CFFTs without and with PVA fiber is nearly similar, the characteristics of the localization are different. The expansion of shear zone for insufficiently basalt FRP (BFRP)-confined concrete is more localized compared to the more homogenized behavior of sufficiently FRP-confined concrete. However, insufficiently BFRP-confined PVA fiber-reinforced concrete exhibits less localized behavior compared to insufficiently BFRP-confined plain concrete, which is due to the influence of the internal fibers on the concrete cracking behavior. At FRP rupture, hoop strains vary along the height and around the perimeter of the specimens, which results in the inability of SGs to consistently capture the actual hoop rupture strain.