1. McCormick School Professor and W.P. Murphy Professor of Civil Engineering and Materials Science, Northwestern Univ., Evanston, IL 60208.
2. Assistant Professor, Institute of Structural Mechanics, Faculty of Civil Engineering, Brno Univ. of Technology, 60200 Brno, Czech Republic.
3. Professor, Institute of Structural Mechanics, Faculty of Civil Engineering, Brno Univ. of Technology, 60200 Brno, Czech Republic.