1. Associate Professor, Dept. of Civil and Environmental Engineering, Norwegian Univ. of Science and Technology, S.P. Andersens veg 5, Trondheim 7491, Norway (corresponding author).
2. Professor, School of Science and Engineering, Reykjavík Univ., Menntavegur 1, Reykjavik IS-101, Iceland; Professor II, Dept. of Mechanical and Structural Engineering and Material Science, Univ. of Stavanger, Stavanger 4036, Norway.
3. Professor Emeritus, Dept. of Civil and Environmental Engineering, Norwegian Univ. of Science and Technology, Høgskoleringen 7, Trondheim 7491, Norway.