1. Ph.D. Student, Dept. of Civil and Environmental Engineering, Univ. of California, Berkeley, Berkeley, CA.
2. State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi’an Jiaotong Univ., Xi’an, China.
3. Chancellor’s Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Berkeley, Berkeley, CA.