1. Assistant Professor, Dept. of Civil Engineering, Bogazici Univ., 34342 Istanbul, Turkey (corresponding author).
2. Professor, Dept. of Civil, Architectural and Environmental Engineering, Illinois Institute of Technology, Chicago, IL 60616.
3. Associate Professor, Dept. of Civil Engineering, Middle East Technical Univ., 06531, Ankara, Turkey.
4. Professor, Dept. of Civil Engineering, Middle East Technical Univ., 06531, Ankara, Turkey.