CFRP Strip Cable Retrofit of RC Frame for Collapse Resistance

A half-scale, three-story, two-bay, and three-span reinforced concrete model frame retrofitted with carbon fiber–reinforced polymer (CFRP) strip cables was tested under sudden removal of two side middle columns in the long direction on the ground floor to study dynamic responses, resisting mechanism, and CFRP retrofit effects. The CFRP strip cables were anchored to concrete slabs by specially designed anchorage. The experimental results are compared with previous tests of the same frame without CFRP retrofit. The comparison shows that the CFRP strip cables were effective in preventing the total collapse of the frame after the loss of columns. With additional CFRP strip cables, the frame structure sustained the applied gravity load as moment-resisting frames without a transition to catenary action. To further demonstrate the effects, the CFRP strip cables were released, causing the frame structure to deflect downward and eventually collapse. A simplified method was proposed to calculate the average strain on CFRP strip cables and a combining resisting mechanism was established to compute the ultimate capacity provided by slabs, beams, and CFRP strip cables.