1. Professor, Dept. of Civil Engineering, National Taiwan Univ., Taipei 106, Taiwan (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, Singapore 117576; and Board Member, Taiwan Building Technology Center (TBTC), National Taiwan Univ. of Science and Technology, Taipei 106, Taiwan.
3. Graduate Student, Dept. of Civil Engineering, National Taiwan Univ., Taipei 106, Taiwan.