This report shows the structural retrofitting of a two-story reinforced-concrete (RC) welfare-facility building in Niigata prefecture, which was built in 2002. During the Chuetsu earthquake in 2004, the first floor window under the bathroom was damaged. Our investigation revealed that the damage was caused by an error in the structural design and insufficient girder strengths. Thus, such RC girders were retrofitted using the beam string structures composing steel members. The stress was reduced by introducing a pushing force to satisfy the allowable stress. This method was simple, easy to install, and economical.
