1. Distinguished Professor, Dept. of Civil Engineering, Hydrotech Research Institute, National Taiwan Univ., Taipei 10617, Taiwan (corresponding author).
2. Ph.D. Candidate, Dept. of Civil Engineering, Hydrotech Research Institute, National Taiwan Univ., Taipei 10617, Taiwan.
3. Dept. of Civil Engineering, Hydrotech Research Institute, National Taiwan Univ., Taipei 10617, Taiwan.
4. Ph.D. Candidate, Univ. of Southern Mississippi, Hattiesburg, MS 39406.