1. Research Associate, Dept. of Civil Engineering (ISBS), Technische Universität Braunschweig, 38106 Braunschweig, Germany.
2. Senior Researcher, Korea Expressway Corporation, Research Institute, Pavement Research Division 50-5, Sancheok-ri, Dongtan-myeon, Hwaseong-si, Gyeonggi-do 445-812, South Korea (corresponding author).