Short and Slender Concrete Columns Internally or Externally Reinforced with Longitudinal Fiber-Reinforced Polymer Composites

Abstract

The goal of this thesis was to investigate the behavior of short and slender concrete columns internally and externally reinforced with longitudinal fiber-reinforced polymer (FRP) composites. The study was divided into two major parts. First part addressed the issues regarding the use of FRP as internal reinforcement for new constructions and the second part focused on external FRP reinforcement for strengthening of existing concrete columns. There is a lack of knowledge and experimental data on the use of longitudinal FRPs as external and internal reinforcement. The contribution of FRP bars in compression is ignored by many design guidelines and the use of longitudinally bonded FRPs in compression is not suggested by guidelines due to lack of experimental test data. There is also lack of knowledge regarding the effect of slenderness and associated parameters (e.g., critical slenderness ratio and flexural stiffness) for the columns. Also, the effectiveness of confinement for eccentrically loaded concrete columns is not well-known. Therefore, this thesis addressed the issues regarding the use of external and internal FRP reinforcement in concrete columns using experimental, analytical, numerical, and statistical approaches. To characterize the compressive behavior of FRP bars as internal reinforcement, three different experimental programs were conducted to include a total of 24 columns, including 10 large-scale and 14 small-scale tests, and 35 compressive FRP bar coupons, in part I of the study. In part II, the use of FRPs as external reinforcement were experimentally assessed by testing a total of 36 column in four different experimental programs, including 6 large-scale tests and 30 small-scale tests. For further investigation, a model was developed in MATLAB for second order analysis of concrete columns reinforced internally or externally with FRPs using one-dimensional finite difference method. The nonlinearity of material and geometry and the effect of eccentricity in confinement were also considered. After required verifications, the model was used to perform a parametric study for different parts of the study and to include 18432 different cases. The model was used for a preliminary reliability-based analysis including 800,000 second-order analysis to assess the reliability corresponding different critical slenderness ratios.