1. Ph.D. Candidate, Dept. of Engineering, Univ. of Cambridge, Trumpington St., Cambridge CB2 1PZ, U.K. (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of California-Berkeley, Berkeley, CA 94720.
3. Project Engineer, Cathie Associates SA/NV, 1831 Diegem, Belgium; formerly, Sharjah Fellow, Dept. of Engineering, Univ. of Cambridge, Cambridge CB2 1PZ, U.K.