1. Structural Engineering Department,University of California, San Diego,San Diego, CA 92093e-mail: zodu@eng.ucsd.edu
2. School of Engineering,Cardiff University,Cardiff CF24 3AA, UKe-mail: zhoux19@cf.ac.uk
3. School of Engineering,Cardiff University,Cardiff CF24 3AA, UKe-mail: PicelliR@cardiff.ac.uk
4. Structural Engineering Department,University of California, San Diego,San Diego, CA 92093;School of Engineering,Cardiff University,Cardiff CF24 3AA, UKe-mail: alicia@ucsd.edu