1. Division of Engineering and Policy for Sustainable Environment, Graduate School of Engineering, Laboratory of Engineering for Maintenance System, Hokkaido Univ., Sapporo, Hokkaido 060-8628, Japan.
2. Associate Professor, Dept. of Civil Engineering, College of Civil Engineering and Architecture, Zhejiang Univ., Hangzhou 310058, China (corresponding author).
3. Professor, Division of Engineering and Policy for Sustainable Environment, Faculty of Engineering, Laboratory of Engineering for Maintenance System, Hokkaido Univ., Sapporo, Hokkaido 060-8628, Japan.