1. PhD Student, Dept. of Civ. and Struct. Engrg., Hong Kong Polytechnic Univ., Kowloon, Hong Kong.
2. Assoc. Prof., Dept. of Civ. and Struct. Engrg., Hong Kong Polytechnic Univ., Kowloon, Hong Kong.
3. Prof., Inst. of Vibration Engrg., Nanjing Univ. of Aeronautics and Astronautics, Nanjing 210016, PRC.