1. R&D Center, Samsung Engineering Co., LTD. 415-10, Wancheon-Dong, Youngtong-Gu, Suwan-city, 443-823, South Korea, and Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon, 305-701, South Korea