One-sided shear retrofit of reinforced concrete beams in existing high-rise buildings

This paper presents the evaluation of one-sided shear retrofit schemes for reinforced concrete (RC) coupling beams in existing buildings. Three full-scale beam Specimens CB1, CB2 and CB3 are planned for cyclic tests. Specimen CB1 represents a RC coupling beam in existing 24-story RC buildings, completed in Taiwan, 2017. Specimens CB2 and CB3 are retrofitted by added stirrups in the increased beam cross section and a bolted a steel plate from only one side of the RC beam, respectively. Test results showed that the shear strengths of the two retrofitted specimens exceeded the force of the RC coupling beam expected at the maximum considered earth-quake (MCE) level. Specimen CB1 exhibited flexural-shear failure during the cycle of 5% drift. Specimens CB2 and CB3 exhibited shear failure during the cycle of 4% drift, and then concrete crushing associated with lon-gitudinal bar buckling in the plastic hinge region. The peak shear forces of the added stirrups in Specimen CB2 and of the added steel plate in Specimen CB3 were 34 and 22% of the total shear forces, respectively, at large drifts. The added stirrups in the increased beam cross section provided larger shear force than the bolted steel plate. Both schemes were used to retrofit RC beams in the existing high-rise buildings in New Taipei City.