1. Senior Researcher, Dept. of Civil Engineering, National Technical Univ. of Athens (N.T.U.A.), 9 Heroon Polytehniou st., Greece 15773.
2. Adjunct Professor, Dept. of Civil Engineering, Univ. of Texas, Austin, TX 78712.
3. C. T. Wells Professor, Dept. of Civil Engineering, Univ. of Texas, Austin, TX 78712.