A unified model for the compressive strength of FRP-confined square and circular concrete columns

It has been gradually recognized in recent years that the corner radius plays a keyrole in the effectiveness of the confinement that is provided to concrete columns by squareshapedFRP jackets. When the corner radius ratio ρ is defined as 2r/b, where r is the corner radiusand 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 naturaland logical that a confined concrete model for columns with a corner radius should degenerateinto a model for circular columns when ρ = 1, and into another for sharp cornered square columnswhen ρ = 0. However, this is not the case in any of the existing models, except for that byMirmiran et al. (1998), which has been overlooked in recent years. Extensive experimental testingon FRP-confined concrete columns that have a continuous variation of ρ from 0 to 1 hasbeen undertaken by the authors. Based on these experimental findings, a rational procedure isproposed in this work for developing a unified strength model for FRP-confined concrete columnsthat have an arbitrary corner radius. The model can be degenerated into the two specialcases of circular columns and sharp cornered square columns when ρ = 1 and 0, respectively. Adatabase has been established by collecting all of the available experimental results from the literaturefor both circular and square columns. Comparisons between the test results and themodel predictions have been made to demonstrate the accuracy of the unified model.