The stress strain response of concrete laterally confined with low and high performance fiber-reinforced cements and polymer composites : a comparative experimental and theoretical study

Abstract

While concrete, steel and Fiber Reinforced Polymer (FRP) jackets are the most commonly used types of jackets in the industry to confine columns, the focus of this research is to study and compare the compressive behavior of concrete cylinders confined with different types of fibrous composites; including Fiber Reinforced Concrete (FRC), Fiber Reinforced Mortar (FRM), and Slurry Infiltrated Fiber Concrete (SIFC). This study will provide a broad understanding of the behavior of the different confinement types used to retrofit columns to resist detrimental loads including blast and impact. The study will compare the compressive stress-strain response of different fibrous confinements to the commonly used ones such as FRP and spirals (SP), by developing empirical models to be used in design. The confinements are classified as either continuous or discrete. Continuous confinement is when the composite is wrapped continuously around the structural members such as FRP, FRC, FRM, and SIFC while in discrete confinements they are spaced at a specific pitch such as spirals (SP) and wire mesh (WIM).The purpose of studying different types of fibrous confinements such as FRC and SIFC is to better understand their response with respect to the continuity and orientation of fibers. As for studying WIM confinement, was to understand the effect of two-fiber orientation as well as their interaction (WIM being the “bounding” case with “fibers” being oriented only in the vertical and the horizontal direction).The ultimate goal of this research is to investigate, understand, and develop the overall stress-strain and load-displacement (i.e. resistance and ductility) response model of columns confined with different fibrous composites. The developed compressive stress-strain behavior will be compared to the exiting Spiral Reinforcement (SP) and FRP confinement used commonly in the industry, to be able to select the most suitable, and appropriate retrofit technique, and to be able to design from an engineering standpoint. This research is achieved through an experimental and analytical investigation Models developed in this work have shown good agreement with experimental data. High Performance Fiber Reinforced Concrete (HPFRC) jackets made with continuous fibers exhibited debonding and multiple cracking leading to softening effects beyond peak and higher strains at rupture, which translates into an increase in ductility, and energy dissipation of the confined column. Varying orientation of fibers in FRC and FRM jackets produce radial tensile stresses on the concrete core resulting in partial confinement, thus weakening the concrete core and developing peak stresses lower than unconfined concrete. However due to fiber pull-out, they have higher ductility and maintain softening effects beyond peak and rupture strains better than unconfined concrete.