1. Postdoctoral Researcher, Dept. of Civil Engineering, KU Leuven, B-3001 Leuven, Belgium (corresponding author). E-mail: ellen.simoen@bwk.kuleuven.be
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Tufts Univ., Medford, MA 02155.
3. Professor, Dept. of Structural Engineering, Univ. of California at San Diego, La Jolla, CA 92093.
4. Associate Professor, Dept. of Civil Engineering, KU Leuven, B-3001 Leuven, Belgium.