1. Protective Technology Research Center, School of Civil and Environmental Engineering, Nanyang Technological Univ., Nanyang Ave., Singapore 639798 (corresponding author). E-mail: cfansc@ntu.edu.sg
2. Engineering Mechanics Research Center, School of Architectural Engineering, Nanchang Univ., Beijing Rd. No. 339, NanChang, China 330029. E-mail: smli@ncu.edu.cn