1. Postdoctoral Fellow, Dept. of Civil Engineering, K.U.Leuven, Kasteelpark Arenberg 40, B-3001 Leuven, Belgium (corresponding author).
2. Postdoctoral Fellow, Dept. of Civil Engineering, K.U.Leuven, Kasteelpark Arenberg 40, B-3001 Leuven, Belgium.
3. Full Professor, Dept. of Civil Engineering, K.U. Leuven, Kasteelpark Arenberg 40, B-3001 Leuven, Belgium.
4. Assistant, Faculty of Engineering of the Univ. of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal.
5. Associate Professor, Faculty of Engineering of the Univ. of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal.