1. Associate Professor, Dept. of Civil Engineering, National Chiao Tung Univ., 1001 Ta Hsuech Rd., Hsin-Chu 300, Taiwan, Republic of China (corresponding author).
2. Postdoctoral Researcher, Dept. of Civil Engineering, National Chiao Tung Univ., 1001 Ta Hsuech Rd., Hsin-Chu 300, Taiwan, Republic of China.