Experimental study of retrofitted reinforced concrete shear wall and concrete-encased steel girders using a new CarbonFlex composite for damage stabilization

Abstract

A bi-axially loaded shear wall and two fatigue-damaged concrete-encased steel girders are experimentally tested using a retrofit technique that utilizes a newly developed composite wrap. The composite, which is being termed “CarbonFlex,” helps to stabilize the propagation of damage, specifically fracture, in retrofitted beams and a shear wall via an energy dissipation mechanism, resulting in significant ductility and confinement, and high-strength sustainability. The CarbonFlex-retrofitted shear wall had been initially damaged to a level corresponding to 40% of its peak strength under bi-axial loading (constant vertical load and quasi-static cyclic lateral load). Following the CarbonFlex-retrofit, the capacity doubled to 80% of its original strength while exhibiting significant ductility and having tremendously improved confinement. The fatigue-damaged beams are retrofitted using conventional carbon–fiber reinforced polymers (CFRPs), and then, separately, using the new prototype CarbonFlex composite. The latter beam sustained over 68% of its peak strength following dissipation of the initial shock energy of the fractured welds of the encased steel girder; the beam also exhibited significant displacement ductility, having an ultimate displacement three times that of its CFRP counterpart.