STRAIN EFFICIENCY FACTOR OF FRP WRAPPED CONCRETE COLUMNS

摘要

This paper explores the strain efficiency factor of circular concrete columns wrapped with fiber reinforced polymer (FRP) composites. Strain efficiency factor accounts for the difference between FRP rupture strains observed in concrete column tests and FRP material rupture strains determined from tensile coupon tests or manufacturer datasheets. A large database including 423 circular concrete specimens wrapped with unidirectional fabrics in hoop direction is gathered from the literature and statistical evaluations are performed. In order to explain the difference and predict strain efficiency factor, the concept of biaxial state of stress in FRP wrap and Tsai-Wu interaction failure envelope are implemented for a rational analytical modeling. For the case of unidirectional FRP wraps, a new parabolic interaction failure envelope instead of elliptical failure envelope of Tsai-Wu is proposed for the analytical modeling to be simplified based on fewer input parameters. Strain efficiency factors predicted by the model are verified with the experimental factors extracted from the database where a relatively good agreement is observed.