This study is intended to get an answer to the question that the adding of side walls to old RC columns is effective to enhance their seismic performance or not. For this purpose, ten half-scale model specimens simulating columns designed by the pre-1971 codes with/without side walls were tested until they collapsed. The tests revealed the side-wall adding increased lateral strength but decreased deformability. Then the earthquake response analyses were conducted for three-story model buildings consisting of the tested columns with/without side walls, where the observed load-deflection relations until collapse were used. The side-wall adding was judged as “advantageous” if the ratio of maximum response drift to drift at collapse became smaller than that of the case without side walls. The side-wall adding was “advantageous” in most examples.
