1. Researcher, GITECO (Construction Technology Research Group), Dept. of Transport, Project and Process Technology, School of Civil Engineering (E.T.S.I.C.C.P.), Univ. of Cantabria (UC), Avenida de los Castros s/n, 39005 Santander, Cantabria, Spain (corresponding author).
2. Professor, Dept. of Transport, Project and Process Technology, School of Civil Engineering (E.T.S.I.C.C.P.), Univ. of Cantabria (UC), Avenida de los Castros s/n, 39005 Santander, Cantabria, Spain.