1. Researcher, Dept. of Civil Engineering, Univ. of Tokyo, 7 Chome-3-1 Hongo, Bunkyo, Tokyo 113-8654, Japan.
2. Graduate Student, Laboratory of Engineering for Maintenance System, Graduate School of Engineering, Hokkaido Univ., 5 Chome Kita 8 Jonishi, Kita Ward, Sapporo, Hokkaido Prefecture 060-0808, Japan.
3. Professor, Laboratory of Engineering for Maintenance System, Faculty of Engineering, Hokkaido Univ., 5 Chome Kita 8 Jonishi, Kita Ward, Sapporo, Hokkaido Prefecture 060-0808, Japan.
4. Associate Professor, College of Civil Engineering and Architecture, Zhejiang Univ., 38 Zheda Rd., Xihu Qu, Hangzhou Shi, Zhejiang Sheng 310027, China (corresponding author).