Calibration of Reduction Factor for Concrete Columns Strengthened with Unidirectional Fiber-Reinforced Wrapping

Abstract

Strengthening with fiber-reinforced polymer (FRP) wrapping is a well-established method of retorifiting or upgrading existing concrete columns. The available test data cooreponding to FRP wrapped concrete columns has expanded significantly due to the growing interest in the application of FRP confinment. However, the reduction factors suggested by the applicable design guidelines were developed more than a decade ago based on a limited data set. In this study, reduction factors for FRP confined concrete columns were calibrated using a reliablity-bsed approach. Approximetaly eight hundred experimental tests of FRP wrapped concrete columns with various thicknesses, modulus of elasticity, ultimate tensile strength, number of FRP layers, column diameter, and column compressive strength were considered in the reduction factor calibration. Multiple reduction factors were suggested based on a practical range of target reliability indices. Also, the reliablity indicies that were used in calibrating the reduction factors in ACI 440 were assessed using the database considered in this study. The analysis results showed that the current reduction factor proposed by ACI 440 is adequate for achieving a target reliablity index of 3.5.