A Unified Model for the Compressive Strength of FRPconfined Square and Circular Concrete Columns

 ABSTRACT

It has been gradually recognized in recent years that the corner radius plays a key role in the effectiveness of the confinement that is provided to concrete columns by squareshaped FRP jackets. When the corner radius ratio ρ is defined as 2r/b, where r is the corner radius and b is the breadth of the cross-section, circular columns are just a special case when ρ = 1. Sharp cornered square columns represent another special case when ρ = 0. It is quite natural

and logical that a confined concrete model for columns with a corner radius should degenerate into a model for circular columns when ρ = 1, and into another for sharp cornered square columnsn when ρ = 0. However, this is not the case in any of the existing models, except for that by Mirmiran et al. (1998), which has been overlooked in recent years. Extensive experimental testing on FRP-confined concrete columns that have a continuous variation of ρ from 0 to 1 has been undertaken by the authors. Based on these experimental findings, a rational procedure is proposed in this work for developing a unified strength model for FRP-confined concrete columns that have an arbitrary corner radius. The model can be degenerated into the two special cases of circular columns and sharp cornered square columns when ρ = 1 and 0, respectively. A database has been established by collecting all of the available experimental results from the literature for both circular and square columns. Comparisons between the test results and the model predictions have been made to demonstrate the accuracy of the unified model.