1. Assoc. Prof., Dept. of Civ. and Struct. Engrg., Res. Ctr. for Urban Environ. Technol. and Mgmt., Hong Kong Polytechnic Univ., Hung Hom, Hong Kong (corresponding author). E-mail: cewchu@polyu.edu.hk
2. Res. student, Dept. of Civ. and Struct. Engrg., Hong Kong Polytechnic Univ., Hung Hom, Hong Kong.