2001.3.24 Geiyo Earthquake hit at Chugoku district in Japan, fortunately the extensive damage and the economic losses did not occur, but two low-rise R/C buildings located at the same site, about 26km north of the epicenter, were damaged. One of them was severely damaged and another was moderately damaged while they were constructed at the same time and had almost similar structural systems. Objective of this study is to explain the reasons why only two buildings were damaged in this area and the damage levels of the buildings were considerably different each other, using nonlinear static analysis taking account of strength degradations due to the shear failure of columns. Agreements between the analytical results and the observed failure patterns were reasonably good in the both damaged buildings. Also, the influences of the low concrete strength on the seismic performance of the building were clarified quantitatively.