1. Assistant Professor, Dept. of Construction Engineering, National Taiwan Univ. of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan (corresponding author).
2. Research Assistant, Dept. of Construction Engineering, National Taiwan Univ. of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan.