1. Ph.D. Student, Dept. of Civil Engineering, Gangneung-Wonju National Univ., Ganwon-Do 210-702, Korea.
2. Associate Professor, Dept. of Civil Engineering, Gangneung-Wonju National Univ., Ganwon-Do 210-702, Korea.
3. Professor, Dept. of Civil Engineering, Gangneung-Wonju National Univ., Ganwon-Do 210-702, Korea (corresponding author).