1. Professor, Dept. of Building and Real Estate, Hong Kong Polytechnic Univ., Block Z, 181 Chatham Rd. South, Hung Hom, Kowloon, Hong Kong, People's Republic of China (corresponding author).
2. Research Associate, Dept. of Building and Real Estate, Hong Kong Polytechnic Univ., Block Z, 181 Chatham Rd. South, Hung Hom, Kowloon, Hong Kong, People's Republic of China.