1. Ph.D. Student, Dept. of Civil Engineering, Kunsan National Univ., 558 Daehak Ro, Kunsan, Jeonbuk 573-701, Republic of Korea.
2. Professor, Dept. of Civil Engineering, Kunsan National Univ., 558 Daehak Ro, Kunsan, Jeonbuk 573-701, Republic of Korea (corresponding author).
3. Graduate Assistant, Dept. of Civil Engineering, Kunsan National Univ., 558 Daehak Ro, Kunsan, Jeonbuk 573-701, Republic of Korea.