1. Postdoctoral Researcher, Dept. of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K. (corresponding author).
2. Professor of Structural Engineering, Dept. of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
3. Emeritus Professor of Structural Engineering, Dept. of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.