1. Project Manager, ZERNA Planen und Prüfen, GmbH, Lise-Meitner-Alee 11, 44801 Bochum, Germany (corresponding author).
2. Research Associate, Institute for Structural Mechanics, Ruhr Univ. Bochum, Universitätsstr. 150 IA 6/126, 44780 Bochum, Germany.
3. Professor, Institute for Structural Mechanics, Ruhr Univ. Bochum, Universitätsstr. 150 IA 6/126, 44780 Bochum, Germany.