1. Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong 999077, P. R. China
2. School of Civil Engineering, Wuhan University, Wuhan 430072, P. R. China
3. Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
4. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 999077, P. R. China