Behavior of FRP-Confined Sand and Cemented Sand under Axial Compression

Abstract

Fiber-reinforced polymer (FRP)-confined concrete tubular columns have been extensively studied, where the design of the column is usually based on stiffness and strength. The ability to sustain large deformations without losing structural integrity is also critical in geotechnical engineering. This paper proposes a novel high-ductility tubular column incorporating glass fiber-reinforced polymer (GFRP). The exterior container of the column is a GFRP jacket, while the infill material is sand or cemented sand. Different specimens are prepared with different infill materials (i.e., sand and cemented sand), and the thickness of the GFRP jacket (i.e., 3 mm, 5 mm, and 7 mm). Axial compression tests are conducted to study the compressive behavior of this novel tubular column with two load types (i.e., load on infill and load on the tube). Optical Frequency Domain Reflectometry (OFDR) technique is adopted to monitor the hoop strain distributions along the height of the columns. Experimental results reveal that the presence of infill material could prevent buckling failure of the hollow tubes, while the confinement effect provided by the GFRP tube significantly enhances the bearing capacity and ductility of the infill material. The FRP-confined cemented sand column exhibits notably increased initial stiffness, but slightly decreased ductility and peak load in comparison to the sand-filled FRP column. With the increase in axial displacement, the stiffness of the infill sand core exceeds that of the cemented sand due to the compressive hardening behavior of the sand. Through the OFDR technique, the deformation profile of the column is precisely delineated, facilitating the assessment of the uniformity of the dilation behavior. Moreover, the analysis-oriented model is adopted to rationally predict the load-strain behavior of FRP-confined cemented sand columns.