1. Dept. of Civil Engineering, Indian Institute of Technology, Guwahati, Guwahati 781 039, Assam, India (corresponding author). E-mail: g_barua@iitg.ernet.in
2. Hoffmann RD, Leeuwerik Sweide 196, 6708 LN Wageningen, The Netherlands. E-mail: mhoffmann@h-rd.org