1. SCI-Aeronautical and Vehicle Engineering, Royal Institute of Technology, KTH Fakturaservice, Box 24075, Stockholm 104 50, Sweden e-mail:
2. Norwegian University of Science and Technology, Hamburg University of Technology, Am Schwarzenberg-Campus 4C, Hamburg 21073, Germany e-mail:
3. Institute for Ship Structural Design and Analysis, Hamburg University of Technology, Am Schwarzenberg-Campus 4C, Hamburg 21073, Germany e-mail:
4. SCI-Aeronautical and Vehicle Engineering, Royal Institute of Technology, KTH Fakturaservice, Box 24075, Stockholm 104 50, Sweden