1. Professor, Dept. of Construction Engineering, National Taiwan Univ. of Science and Technology, #43, Sec. 4., Keelung Rd., Taipei 106, Taiwan, ROC.
2. Research Assistant, Dept. of Construction Engineering, National Taiwan Univ. of Science and Technology, #43, Sec. 4., Keelung Rd., Taipei 106, Taiwan, ROC (corresponding author).