Modeling of RC hollow square columns wrapped with CFRP under shear-type load

ABSTRACT

Concrete bridges including hollow piers have been constructed throughout the world where high seismic actions and natural boundaries required high elevation infrastructures.Bridge piers designed in accordance with old design codes suffered severe damage during recent seismic events, caused by insufficient shear or flexural strength, low ductility and inadequate reinforcement detailing. The FRP strengthening interventions are intended to upgrade seismic capacity in terms of strength and ductility. The proposed confinement model, coupled with the proposed computation algorithm, is able to predict the fundamentals of the behavior of the hollow square members confined with FRP both in terms of strength and ductility, tracing the occurrence of the brittle mechanisms, namely concrete cover spalling and reinforcement buckling (liable of the failure mode of hollow members), the evolution of stresses and strains in the concrete and in the confinement jacket, allowing to evaluate at each load step the multiaxial state of stress and eventually the failure of concrete or the failure of external reinforcement. The main output of the proposed model is also the assessment of the member deformability in terms of both curvature and displacement ductility. Results of theoretical analyses and experimental tests (experimental data available in literature) showed that a good agreement was achieved.