1. Department of Civil and Earth Resources Engineering, Kyoto University, Kyotodaigaku Katsura, Nishikyo-ku, Kyoto 615-8540, Japan
2. Department of Civil Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
3. Yokogawa Bridge Corporation, 27 Yamano-cho, Funabashi, Chiba 273-0026, Japan
4. Department of Civil Engineering, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan