1. Lecturer, Dept. of Civil Engineering and Geomatics, Cyprus Univ. of Technology, Limassol, 3036, Cyprus.
2. Reader in Nonlinear Mechanics, Dept. of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, U.K.
3. Lecturer, Lehrstuhl für Kontinuumsmechanik und Materialtheorie, Institut für Mechanik, Technische Univ. Berlin, 10587 Berlin, Germany (corresponding author).