[1] Univ Texas, Dept Civil Engn, Austin, TX 78712 USA
[2] Ecole Normale Super, Dept Genie Civil, Cachan, France
[3] Univ Calif Berkeley, Dept Civil & Environm Engn, Berkeley, CA 94720 USA
[4] Lafarge, Cent Rech Lab, F-38291 St Quentin Fallavier, France
[5] Univ Calif Berkeley, Lawrence Berkeley Lab, Ctr Xray Opt, Berkeley, CA 94720 USA