A seismic reinforcement efficiency evaluation index is proposed to select the optimal seismic reinforcement plan considering seismic performance, construction costs, and environmental impact. Focusing on seismic reinforcement of existing RC buildings, construction costs and environmental impacts are normalized to those related to reconstruction. Three types of common strengthening techniques were studied: RC shear walls, steel braces, and CLT walls. The evaluation results showed that using RC shear walls was the most cost-efficient, while CLT walls had the smallest environmental impact, suggesting that the most efficient retrofitting plan depends on the weighting assigned to costs and environmental impact.
