1. Postdoctoral Research Fellow, Univ. of Texas at Austin, Austin, TX 78712 (corresponding author).
2. Former Graduate Research Assistant, Univ. of Texas at Austin, Austin, TX 78712.
3. Former Graduate Research Assistant, Washington State Univ., Pullman, WA 99164.
4. L. P. Gilvin Professor in Civil Engineering, Univ. of Texas at Austin, Austin, TX 78712.
5. Professor and Dean, College of Engineering, Colorado State Univ., Fort Collins, CO 80523.