1. Lecturer, School of Civil Engineering and the Environment, Univ. of Southampton, Southampton, SO17 1BJ, England.
2. Associate Professor, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, China (corresponding author).
3. Engineer, Mott MacDonald, Croydon, CR0 2EE, England.
4. Professor, School of Civil Engineering and the Environment, Univ. of Southampton, Southampton SO17 1BJ, England.