1. Department of Computer Science and Department of Civil and Environmental Engineering, Portland State University, P.O. Box 751, Portland, OR 97207-0751.
2. Department of Civil and Environmental Engineering, Portland State University, P.O. Box 751, Portland, OR 97207-0751.
3. Department of Civil and Environmental Engineering, College of Engineering, California Polytechnic State University, Building 192, Room 301, San Luis Obisbo, CA 93407.