1 Student member of JSCE, Ph.D. Student, Dept. of Civil and Environmental Engineering, Nagaoka University of Technology (1603-1, Kamitomioka, Nagaoka, Niigata 940-2188, Japan) 2 Member of JSCE, Dr. Eng., Professor, Dept. of Civil and Environmental Engineering, Nagaoka University of Technology (1603-1, Kamitomioka, Nagaoka, Niigata 940-2188, Japan) 3 Member of JSCE, Dr. Eng., Adjunct Professor, Chongqing Jiaotong University, Chongqing, China