Progressive collapse performance of shear strengthened RC frames by nano CFRP

To investigate the effect of nano carbon-fiber-reinforced polymer (nano CFRP) on retrofitting reinforced concrete (RC) structures, this article presented the progressive collapse performance of two half-scale four-bay RC frames including one control specimen S1 and specimen S2 with nano CFRP retrofitting beam ends. The progressive collapse performance was discussed by comparing crack patterns, failure mode, load-displacement curves, horizontal displacement, strains, and rotational and energy dissipation capacity. The test results demonstrated that nano CFRP did not change the ductile beam-hinge failure mode, but improved the load-bearing capacity and ductility efficiently, and postpone shear failure of the joint core region obviously. Due to the insufficient development of plastic hinges limited by nano CFRP, S2 failed to enter catenary action, which revealed its own defects in anti-progressive collapse. It was shown that the retrofitting strategy using nano CFRP can substantially improve the mechanical characteristics and implement the strong column-weak beam failure mode.