1. Research Scholar, Trinity College, Cambridge CB2 1TQ, U.K. (corresponding author).
2. University Lecturer, Laing O’Rourke Centre for Construction Engineering and Technology, Dept. of Engineering, Univ. of Cambridge, Trumpington St., Cambridge CB2 1PZ, U.K.
3. University Senior Lecturer, Dept. of Engineering, Univ. of Cambridge, Trumpington St., Cambridge CB2 1PZ, U.K.