1. Lecturer, Dept. of Civil and Structural Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523.
3. Professor Emeritus, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523.