Experimental studies on behavior of failed CRB750 steel bars reinforced concrete beams retrofitted with steel plate

Abstract

The CRB750 steel bar is a new cold-rolled ribbed bar, which has the yield strength as high as 750 MPa and the ultimate elongation as high as 27%. A failed concrete beam reinforced with CRB750 steel bars could be continuously used as a structural component after retrofitted with steel plate at the beam compression zone, for the CRB750 steel bars might have a great potential load carrying capacity at the failure state of concrete in the compression zone crushed. The temporary use the failed structural components is very important for the rescue work in a hazard attacked region.This paper presented test results of 5 RC beams reinforced by CRB750 and 1 RC beam reinforced by HRB400. These beams were loaded to failure and then retrofitted with steel plate at the compression region. Then the retrofitted beams were tested again to show whether it could be temporary used in emergency, such as for the temporary transportation requirement of a concrete bridge beam in the seismic attacked area. Presented results included the flexural capacity, deflection, failure modes, stiffness, and ductility of the original RC beams and crushed RC beams retrofitted with steel plates at the compression region. The reinforcement ratio was changed by changing the section area and the number of rebar. Analysis results showed that the crushed CRB750 steel bars reinforced RC beams retrofitted with steel plate had much higher bending moment capacity and ductility than the original beams if they were over-reinforced. The design equations provided in GB 50010-2010 and GB 50367-2013 could be used to calculate the ultimate bending moment resistance of the crushed RC beams reinforced by CRB750 steel bars retrofitted by steel plate.