[1] Southwest Jiaotong Univ, Sch Civil Engn, Chengdu 611756, Sichuan, Peoples R China
[2] Univ Reading, Sch Appl Math, Reading RG6 6AH, Berks, England
[3] Mt Holyoke Coll, Dept Math & Stat, South Hadley, MA 01075 USA
[4] Southern Methodist Univ, Dedman Coll Humanities & Sci, Dallas, TX 75205 USA