Flexural behavior of circular concrete filled FRP shells

A new structural system has been developed that combines a fiber-reinforced polymer (FRP) shell with a concrete core for use as bending members in civil structural applications. The external fiber-reinforced shell in this system replaces the functions of steel rebar in conventional reinforced concrete, namely, tension carrying capacity, shear resistance, and confinement of the concrete core. This paper attempts to characterize the response of such a hybrid composite concrete system under flexural loading. Compression behavior is discussed with emphasis on understanding the dilation behavior of the concrete core. Models are proposed to predict the longitudinal, hoop, and shear strains in the FRP shell. Large-scale experimental validation of the models is presented.