1. Professor, Univ. of Illinois at Urbana-Champaign, 3129e Newmark Civil Engineering Laboratory, 205 N. Mathews, Urbana, IL 61801.
2. Research Assistant, Univ. of Illinois at Urbana-Champaign, 3109 Newmark Civil Engineering Laboratory, 205 N. Mathews, Urbana, IL 61801.