1. Professor, Dept. of Civil Engineering, National Cheng Kung Univ., Tainan, Taiwan 701, R.O.C.
2. Associate Professor, Dept. of Civil Engineering, National Chiao Tung Univ., Hsinchu, Taiwan 30050, R.O.C.
3. Research Assistant, Dept. of Civil Engineering, National Cheng Kung Univ., Tainan, Taiwan 701, R.O.C.