Taiwan-Japan Collaborative Retrofit Tests on RC Columns Subjected to High Axial Force and Double-Curvature Moment

Taiwan-Japan Collaborative Retrofit Tests on RC Columns Subjected to High Axial Force and Double-Curvature Moment

Recent studies indicated that under a severe earthquake, some existing RC residential buildings designed according to the old building codes in Taiwan and Japan could be damaged severely. Shear failure of columns in lower stories always caused severe damages and are identified as one of the most possible sources of seismic hazard. This paper focuses on the retrofit techniques for rectangular RC columns using various kinds of retrofit schemes. The objectives of this study include:(1) collecting additional information on seismic retrofit of rectangular columns using the PC-bars retrofit scheme, which is a fast and efficient dry-retrofit method and can be applied successfully as an emergency retrofit,(2) validating existing retrofit schemes(steel jacketing and CFRP wrapping), and(3) seeking other retrofit schemes(CFRP wrapping + CFRP anchorage bolts) for rectangular RC columns. For the purpose of exchanging research results, Taiwan-Japan collaborative retrofit tests were launched at the National Center of Research on Earthquake Engineering(NCREE) in 2005. With well-designed test frame, specimens of RC columns were subjected to high axial force and double-curvature moment during the cyclic loading tests. A total of eight full-scale specimens were constructed and tested, one as-built benchmark specimen, and the other seven specimens were retrofitted with different kinds of methods. Test results demonstrated that the shear failure of the rectangular RC columns can be prevented by all the tested retrofit schemes. The seismic performance of the rectangular RC columns can be enhanced significantly by the properly-constructed octagonal steel jacket and by CFRP wrapping plus CFRP anchorage bolts.