1. Lect., Dept. of Appl. Mech., Bengal Engrg. Coll., Deemed University, Howrah 711 103, India (corresponding author). E-mail: basubec@ hotmail.com
2. Asst. Prof., Dept. of Civ. Engrg., Bengal Engrg. Coll., Deemed University, Howrah 711 103, India. E-mail: schak@becs.ac.in