1. Ph.D. Student, Dept. of Civil and Construction Engineering, National Taiwan Univ. of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 10607, Taiwan.
2. Assistant Professor, Dept. of Civil and Construction Engineering, National Taiwan Univ. of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 10607, Taiwan (corresponding author).