Unified Strength Model for Square and Circular Concrete Columns Confined by External Jacket

When the corner radius ratio rho is defined as 2r/b (corner radius divided by half breadth of column), circular and sharp cornered square columns are just two special cases when rho=1 and 0, respectively. It is quite logical that a confined concrete strength model for columns with a corner radius should degenerate into a model for circular and sharp cornered square columns when rho=1 and 0, respectively. However, this is not the case in any of the existing models, except for the early one by Mirmiran in 1998. Extensive experimental testing on fiber-reinforced polymer (FRP)-confined concrete columns that have a continuous variation of rho from 0 to 1 has been undertaken by the writers. Based on the experimental findings, a rational procedure is proposed for developing a unified strength model for FRP-confined concrete columns with an arbitrary corner radius. A comprehensive database has been established by collecting all of the available experimental results from the open literature for evaluation of the unified model. The proposed procedure is applicable to concrete columns confined not only by FRP materials but also other materials such as steel plates.