American Society of Civil Engineers


Causes of Variation in Construction Project Task Starting Times and Duration


by Brad W. Wambeke, M.ASCE, (Lieutenant Colonel, Ph.D. student, Academy Professor, U.S. Army, Dept. of Civil, Construction, and Environmental Engineering, North Carolina State Univ., Raleigh, NC 27695-7908; Dept. of Civil and Mechanical Engineering, United States Military Academy, West Point, NY 10996. E-mail: bwwambek@ncsu.edu), Simon M. Hsiang, (Derr Professor, Industrial Engineering, Texas Tech Univ., Lubbock, TX 79409; formerly, Associate Professor, Fitts Dept. of Industrial and Systems Engineering, North Carolina State Univ., Raleigh, NC 27695-7908. E-mail: simon.hsiang@ttu.edu), and Min Liu, (corresponding author), A.M.ASCE, (Assistant Professor, Dept. of Civil, Construction, and Environmental Engineering, North Carolina State Univ., Raleigh, NC 27695-7908 E-mail: min_liu@ncsu.edu)

Journal of Construction Engineering and Management, Vol. 137, No. 9, September 2011, pp. 663-677, (doi:  http://dx.doi.org/10.1061/(ASCE)CO.1943-7862.0000342)

     Access full text
     Purchase Subscription
     Permissions for Reuse  

Document type: Journal Paper
Section Heading: Labor and Personnel Issues
Abstract: In this research, variation is defined as the time difference between what was planned and what actually happened in terms of task starting times and duration. Variation in construction tasks is important as it can impact productivity performance. Construction projects consist of a large number of interdependent tasks. When the starting time and/or duration of one task varies, it can affect other downstream tasks and result in disruptions to the schedule and/or decreased productivity. The construction process is complex and involves numerous people with different levels of responsibility, which makes identifying the root causes of the variation difficult. A nationwide survey was administered to workers, foremen, and project managers to identify the most prevalent causes and magnitude of both starting time and task duration variation. Fifty individual causes of variation were divided into eight categories: prerequisite work, detailed design/working method, labor force, tools and equipment, material and components, work/job site conditions, management/supervision/information flow, and weather or external conditions. This research examined the similarities and differences in perceptions between craft workers, foremen, and project managers in terms of starting time and task duration variation. The top eight causes of starting time variation and top nine causes of task duration variation were identified. The research also quantitatively analyzed the underlying structure of the causes of variation using factor analysis. This was done by grouping the 50 individual causes into nine orthogonal factors that represent the underlying structure of the affecting causes. The findings will help construction project managers and field managers focus on the root causes of variation during planning in order to develop effective strategies to reduce variation and improve project productivity performance.


ASCE Subject Headings:
Labor
Productivity
Construction management
Time factors

Author Keywords:
Labor productivity
Construction
Variation
Factor analysis