1. Postdoctoral Fellow, Dept. of Civil, Architectural and Environmental Engineering, Univ. of Texas at Austin, 1 University Station D9300, Austin, TX 78712 (corresponding author).
2. Assistant Professor, School of Civil and Environmental Engineering, Urban Design and Studies, Chung-Ang Univ., Seoul 156-756, Korea.
3. Postdoctoral Fellow, Dept. of Civil, Architectural and Environmental Engineering, Univ. of Texas at Austin, 1 University Station D9300, Austin, TX 78712.
4. Professor, Dept. of Civil and Environmental Engineering, Texas Tech Univ., 10th and Akron, Lubbock, TX 79409.