16 th World Conference on Earthquake, 16WCEE 2017 Santiago Chile, January 9th to 13th 2017 Paper N° 611 (Abstract ID) Registration Code: S-O1461743463 FORMULA FOR SHEAR STRENGTH OF CYLINDRICAL SHEAR-KEY APPLIED SEISMIC RETROFITTING T. Abe (1) , T. Hiwatashi (2) , M. Kubota (3) , Y. Takase (4) , K. Katori (5) (1) Reserch Institute of Tecnology, TOBISHIMA Corporation, Japan, takahide_abe@tobishima.co.jp (2) Senior Researcher, Reserch and Development Center, TOA Corporation, Japan, t_hiwatashi@toa-const.co.jp (3) Reserch Institute of Tecnology, TOBISHIMA Corporation, Japan, masaharu_kubota@tobishima.co.jp (4) Associate Professor, College of Environmental Technology, Muroran Institute of Technology, Japan, y.takase@mmm.muroran-it.ac.jp (5) Professor, Department of Architecture, Faculty of Science & Engineering, Toyo University, Japan, katori@toyonet.toyo.ac.jp Abstract In the seismic retrofitting of an existing concrete structure, the surface of the structural frame is chipped to improve the integrity between the existing frame and retrofitting member. But, quantitatively evaluating strength of these joints are difficult because the concavo-convex shape is influenced by construction worker. Therefore, the authors developed a new joint referred to as the cylindrical shear-key. The cylindrical shear-key is made by filling a cylindrical core on the concrete surface with grout or concrete, and resists shear forces as a shear-key. Creating a uniform shape is expected to enable quantitative strength evaluation. In this study, direct shear tests were conducted using a cylindrical shear-key to investigate the fundamental performance of the shear-key. Then, based on the test results, an formula was developed for evaluating the strength of cylindrical shear-key, and it was shown that the maximum strength could be quantitatively evaluated accurately. And cylindrical shear-key is can contribute to the progression of seismic retrofitting. Keywords: Concrete surface roughening, Bearing resistance, Shear-key, Earthquake retrofitting, Shear strength