1. Professor, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634-0911 (corresponding author).
2. Research Assistant, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634-0911.
3. Technical Staff, ANSYS, Inc., Probabilistic Design and Optimization Group, Southpointe, 275 Technology Dr., Canonsburg, PA 15317.