1. Head, Civil Engineering School, Universidad Técnica Particular de Loja, Jorge Anibal Páez N47-364 y Gonzalo Salazar, Quito 170501, Ecuador.
2. Lecturer, Dept. of Civil and Environmental Engineering, Univ. of Auckland, 20 Symonds St., Auckland 1072, New Zealand (corresponding author).
3. Professor and Head, Dept. of Construction, Engineering and Management, Pontificia Universidad Católica de Chile, Casilla 306, Correo 22, Santiago, Chile.