1. Department of Mechanics of Materials and Constructions (MEMC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium
2. Department of Mechanics of Materials and Constructions (MEMC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium,