1. Univ. Limoges, CNRS, XLIM, UMR 7252, F-87000 Limoges, France
2. Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, MN 55406, USA
3. Department of Civil and Environmental Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA