Investigation of a Hybrid Technique for Seismic Retrofitting of Bare Frames

To enhance the lateral strength, stiffness, and ductility of reinforced concrete bare frames, which are vulnerable to large seismic excitation, a simple, convenient, economic, and effective retrofit concept of cast-in-site partial or full, thick hybrid wall using additional concrete sandwiched by steel plates and high-strength steel bar prestressing is proposed in this paper. The frames were retrofitted by casting additional wing-walls adjacent to columns (referred to as opening-type wing-walls) and additional panel-walls into bare frames (referred to as non-opening-type panel-walls). The frames thus retrofitted were experimentally investigated under simultaneous cyclic lateral forces and a constant vertical load. It was verified that the proposed retrofit technique for bare frames is effective in terms of increasing lateral strength, stiffness, and ductility. For the analytic assessment of the proposed retrofit technique, design guidelines to calculate flexural strength, shear strength, and lateral force resistance capacity are suggested.