1. Professor of Engineering, Dept. of Construction Engineering and Management, Pontificia Universidad Católica, Casilla 306, Santiago 22, Chile.
2. Professor of Engineering, Dept. of Industrial and Systems Engineering, Pontificia Universidad Católica, Casilla 306, Santiago 22 Chile (corresponding author).
3. Research Assistant, Dept. of Construction Engineering and Management, Pontificia Universidad Católica, Casilla 306, Santiago 22, Chile.