1. Professor, Dept. of Architecture and Architectural Engineering, Seoul National Univ., Seoul 151-742, Korea (corresponding author).
2. Graduate Student, Dept. of Architecture and Architectural Engineering, Seoul National Univ., Seoul 151-742, Korea.
3. Former Graduate Student, Dept. of Architecture and Architectural Engineering, Seoul National Univ., Seoul 151-742, Korea.
4. Senior Researcher, Dept. of Steel Solution Marketing, POSCO, Incheon, Korea.