1. Associate Professor, Institute of Lowland Technology, Saga Univ., 1 Honjo, Saga 840-8502, Japan.
2. Challis Professor, Dept. of Civil Engineering, The Univ. of Sydney, New South Wales 2006, Australia.
3. Professor, Institute of Lowland Technology, Saga Univ., 1 Honjo, Saga 840-8502, Japan.