1. Staff Scientist, Institute for Structural Analysis, Graz Univ. of Technology, Lessingstraße 25/II, A-8010 Graz, Austria (corresponding author).
2. Research Assistant, Institute for Structural Analysis, Graz Univ. of Technology, Lessingstraße 25/II, A-8010 Graz, Austria.
3. Professor, Institute for Structural Analysis, Graz Univ. of Technology, Lessingstraße 25/II, A-8010 Graz, Austria.