1. Senior Lecturer, Dept. of Civil Engineering, Rajamangala Univ. of Technology Tawan-Ok, 225 Phayathai Rd., Pathum-Wan, Bangkok 10330, Thailand (corresponding author).
2. Senior Lecturer, Dept. of Civil and Structural Engineering, Univ. of Sheffield, Sir Frederick Mappin Bldg., Mappin St., Sheffield S1 3JD, U.K.
3. Professor, Dept. of Civil and Structural Engineering, Univ. of Sheffield, Sir Frederick Mappin Bldg., Mappin St., Sheffield S1 3JD, U.K.