1. Ph.D. Candidate, School of Civil Engineering, Polytechnic Univ. of Madrid, Profesor Aranguren, w/n., 28040 Madrid, Spain (corresponding author).
2. Professor, School of Civil Engineering, Polytechnic Univ. of Madrid, Profesor Aranguren, w/n., 28040 Madrid, Spain.
3. Assistant Professor, Building Technology Program, School of Architecture and Planning, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139.