1. Senior Researcher, Tecnalia Research and Innovation, Parque Cientifico y Tecnologico de Bizkaia, C/ Geldo, Edificio 700, 48160 Derio, Spain (corresponding author).
2. Graduate Student Researcher, Dept. of Structural Engineering, Univ. of California, San Diego, 9500 Gilman Dr., MC0085, La Jolla, CA 92093-0085.
3. Professor, Dept. of Structural Engineering, Univ. of California, San Diego, 9500 Gilman Dr., MC0085, La Jolla, CA 92093-0085.