Development and behavior of a new hybrid column for civil infrastructure systems

Steel reinforced concrete column structures undergo significant deterioration due to environmental effects and natural disasters. To achieve more durable and economical structures, a new type of structural concrete column was developed for new construction. The columns are made of a concrete core encased in PVC tubes reinforced with fiber reinforced polymer (PVC-FRP). The PVC tubes are externally reinforced with continuous impregnated fiber in the form of hoops at different spacings. The PVC acts as formwork and a protective jacket, while the FRP hoops provide confinement to the concrete. The volume of fiber of this concrete reinforcing scheme is very small compared with other existing confinement methods such as FRP tubes and jackets. The present study is an analytical and experimental investigation of the proposed concrete column. The focus of this research is on the confinement of concrete with PVC-FRP tubes, comparing the behavior of PVC-FRP tube confined concrete with current FRP confining methods, quantifying the effect of axial reinforcement on the behavior of PVC-FRP tube confined concrete, investigating the durability characteristics of PVC-FRP tube confined concrete and developing design procedures for PVC-FRP tube confined concrete.; Specimens were manufactured, and axial compression tests were conducted for short PVC-FRP confined concrete columns. The behavior of those specimens was investigated, and the effect of volume of fiber, type of fiber, and axial reinforcement was analyzed.; In order to quantify the effect of environmental exposures on the responses of concrete confined with PVC-FRP tubes, specimens were subjected to medium and long-term wet/dry and freeze/thaw exposures. The effect of these environmental exposures on the strength, deformation, ductility and stress-strain responses was discussed.; Based on the test results, equations to predict the ultimate strength and strain of concrete confined with PVC-FRP were developed, and a confinement model for PVC-FRP confined concrete was proposed. The proposed models were verified against experimental results. Good correlation was obtained.; New design equations for PVC-FRP were developed. The proposed equations take into consideration the volume of fiber required, the level of the axial loading, the required ductility and the axial reinforcement. It was concluded that the proposed design equations predict the experimental results well.