1. School of Civil Engineering, Chongqing University, Chongqing 400045, P. R. China
2. MOE Key Laboratory of New Technology for Construction of Cities in Mountain Area, Chongqing University, P. R. China
3. School of Civil Engineering and Architectural, Chongqing University of Science and Technology, Chongqing 401331, P. R. China
4. School of Civil Engineering, Tsinghua University, Beijing 100084, P. R. China