1. Dept. of Civil Engineering, Indian Inst. of Technology Kharagpur, West Bengal 721 302, IN, e-mail: anushkc@civil.iitkgp.ernet.in
2. Dept. of Civil Engineering, Indian Inst. of Technology Kharagpur, West Bengal 721 302, IN (Corresponding author), e-mail: kpb@civil.iitkgp.ernet.in