1. Post-Doctoral Fellow, McMaster Univ. Center for Effective Design of Structures, Hamilton ON, Canada L8S 4L7; on leave, Structural Engineering Dept., Ain Shams Univ., Cairo, Egypt.
2. Professor, Dept. of Civil and Architectural Engineering, Drexel Univ., Philadelphia, PA, 19104.
3. Professor, Dept. of Civil and Architectural Engineering, Drexel Univ., Philadelphia, PA 19104.