[1] Northwestern Univ, Dept Civil & Environm Engn, Evanston, IL 60208 USA
[2] Northwestern Univ, Dept Mech Engn, Evanston, IL 60208 USA
[3] Tsinghua Univ, Dept Engn Mech, FML, Beijing 100084, Peoples R China
[4] Univ Illinois, Dept Mech Sci & Engn, Urbana, IL 61801 USA