1. M.Eng Cadidate, Dept. of Civil Engineering Science, Univ. of Johannesburg, Auckland Park Kingsway Campus, P.O. Box 524, Johannesburg 2006, South Africa (corresponding author).
2. Associate Professor, Dept. of Civil Engineering Science, Univ. of Johannesburg, Auckland Park Kingsway Campus, P.O. Box 524, Johannesburg 2006, South Africa.
3. Senior Lecturer, Dept. of Civil Engineering Science, Univ. of Johannesburg, Auckland Park Kingsway Campus, P.O. Box 524, Johannesburg 2006, South Africa.