Stress-Strain Behavior of Circular Concrete Columns Partially Wrapped with FRP Strips

Abstract

Fiber-reinforced polymer (FRP) jacketing or wrapping has become an attractive strengthening technique for concrete columns. Within this strengthening technique, FRP composites are wrapped around the concrete column with the fibers in the jacket being oriented in the hoop direction. In practice, the FRP jackets can be either continuous or discontinuous along the column height and thus the resulting column is referred to as fully or partially wrapped FRP-confined concrete columns. Existing research has demonstrated that the partially strengthening technique by discrete FRP strips is a promising and economic alternative to the fully FRP strengthening technique. Although a number of experimental investigations have been conducted on partially wrapped FRP-confined concrete columns, the stress-strain behavior of FRP-confined concrete in partially wrapped concrete columns is not yet understood. This paper presents an experimental program to investigate the axially compressive behavior of circular concrete columns partially wrapped with FRP strips. The test results are presented and compared with the predictions from a typical analysis-oriented stress-strain model to examine its reliability and accuracy. It has been demonstrated that the model provides reasonably accurate predictions of the ultimate axial stress of partially FRP-confined concrete while it usually underestimates the ultimate axial strain.