Shape Modification with Expansive Cement Concrete for Confinement with FRP Composites

Synopsis: To improve the confinement effectiveness of FRP composites for square and rectangular columns, shape modification is performed by using prefabricated FRP shells combined with expansive cement concrete. Chemical post-tensioning using expansive cement concrete is used to change the FRP confinement from “passive” to “active”. Experimental results are presented demonstrating the effectiveness of this method. An analytical stress-strain model is developed for shape-modified FRP-confined columns with expansive cement concrete which is based on the modified Willam-Warnke plasticity model, the Popovics general stress-strain concrete model, and the dilatancy behavior obtained from the present study. This model is implemented by an incremental approach which accounts for the variable FRP confinement during the loading process. The analytical results show satisfactory agreement with the experiments.