1. Postdoctoral Researcher, Dept. of Civil Engineering, Gangneung-Wonju National Univ., Jukheon-gil 7, Gangneung-si, Gangwon-do 210-702, South Korea.
2. Professor, Dept. of Civil Engineering, Gangneung-Wonju National Univ., Jukheon-gil 7, Gangneung-si, Gangwon-do 210-702, South Korea (corresponding author).