1. Assistant Professor, Dept. of Civil and Ecological Engineering, I-Shou Univ., 840 Kaohsiung, Taiwan. E-mail: chengjf@isu.edu.tw
2. Professor, Dept. of Civil Engineering, National Cheng Kung Univ., 701 Tainan, Taiwan (corresponding author). E-mail: yusin@mail.ncku.edu.tw