1. Graduate Student, Faculty of Engineering, Lab of Engineering for Maintenance System, Hokkaido Univ., Sapporo 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, Faculty of Engineering, Lab of Engineering for Maintenance System, Hokkaido Univ., Sapporo 060-8628, Japan.