Elastic Fiber Ropes of Ultrahigh-Extension Capacity in Strengthening of Concrete through Confinement

This paper deals with the experimental investigation of the use of low modulus vinylon and polypropylene fiber ropes as external confining reinforcements on standard concrete cylinders. Vinylon has a higher modulus of elasticity than polypropylene, whereas the latter has ultrahigh tensile deformation at failure. Ropes require no use of impregnating resins or mortars. The research examines low concrete strength columns in three levels of rope confinement, subjected to monotonic or cyclic loading. The effectiveness of the rope composite reinforcements is assessed by the resulting axial stress versus axial and lateral strain behavior. The elaboration also includes the stress and strain values both at 3% axial strain and at ultimate strain. Suitable fiber rope confinement may improve plain concrete strength by a factor higher than 6.6 and provide an axial strain ductility higher than 40. No column wrapped by polypropylene fiber ropes reaches fiber fracture. The performance of the retrofitted columns is discussed with respect to the fiber-reinforced polymer sheet confinement.