1Institute of Structural Mechanics, Bauhaus-Universität Weimar, Marienstr. 15, D-99423 Weimar, Germany
2Institute of Structural Mechanics, Bauhaus Universität-Weimar, Marienstr 15, D-99423 Weimar, Germany
3School of Civil, Environmental and Architectural Engineering, Korea University, 136-713 Seoul, Republic of Korea