1. Professor, Computational Solid and Structural Mechanics Laboratory, Dept. of Civil Engineering, Hanyang Univ., Seoul 133-791, Korea.
2. Ph.D. Student, Computational Solid and Structural Mechanics Laboratory, Dept. of Civil Engineering, Hanyang Univ., Seoul 133-791, Korea.
3. BK Contract Professor, Computational Solid and Structural Mechanics Labaoratory, Dept. of Civil Engineering, Hanyang Univ., Seoul 133-791, Korea.
4. Boyd Professor, Computational Solid Mechanics Laboratory, Dept. of Civil and Environmental Engineering, Louisiana State Univ., Baton Rouge, LA 70803 (corresponding author).