Flexural Strength and Behavior of Circular Sand-coated Concrete-filled FRP Tubes under Cyclic Load

摘要

This paper investigates experimentally the effect of sand coating bond enhancer on the flexural behavior of circular concrete-filled FRP tube (CFFT) by testing two full-scale CFFT cantilevers under lateral cyclic load. The full-bond between concrete and any kind of reinforcement is one of the main factors affecting on its flexural behavior. Limited research has investigated the bond effect on CFFT flexural behavior. The bond between the concrete core and the interior surface of the FRP tube is the main parameter of this study. Embedded-concrete strain gauges were used to measure the strain values inside the concrete core, then compared with the strain values measured from the electric strain gauges installed on the tube outer surface. The observed experimental results illustrate that the sand coating increases the flexural strength and stiffness of circular CFFT members. No slippage was observed on the sand-coated specimen; while 6 mm (0.24 in) slippage was measured on the specimen without sand coating. The internal and external strain curves are identical for the sand-coated specimen; while these curves are incompatible for the specimen without sand coating. The experimental results demonstrate the significance of investigating the bond effect and the sand coating contribution to improve the bond between the concrete core and the FRP tube, and assure a good composite action under flexural loads.