Modeling the dynamics of highway construction equipment downtime | |
| Author | Thanapun Prasertrungruang |
| Subject(s) | Modeling Roads--Design and construction |
| Note | The degree of Doctor of Engineering in Construction, Engineering and Infrastructure Management, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | Downtime resulting from machine breakdown invariably has a substantial impact on the performance of construction projects and companies as a whole, especially to contractors with heavy investment in equipment. As managing construction equipment is tightly connected to various activities and parties inside as well as outside of the firm, failure to account for the dynamic characteristics (e.g. cause-effect relationships, multiple feedback loops, nonlinear relationships, and time-delayed responses) of equipment management practices invariably causes downtime to be even more severe. To date, few studies have been made to investigate the causes and consequences of downtime. Attempts to highlight the dynamic behaviors of downtime, particularly in construction equipment, are rarely found as well. The aims of this study are divided into two major parts: 1) to investigate current practices and problems in heavy equipment management and to identify practices capable of alleviating equipment management problems for highway contractors, and 2) to highlight the dynamics of heavy equipment management practices and downtime in highway contractors and then recommend policies for equipment performance improvement. The first objective is the preliminary and exploratory study of this research to fully understand the problems and practices in equipment management of Thai highway contractors. The second objective is considered as the main purpose of the study, which was formulated and conducted based upon the results from the first objective. To achieve the first objective, a questionnaire survey was conducted to collect data on equipment management practices and problems from 162 Thai highway contractors. Statistical techniques, including one-way ANOVA, correlation test, and Structural Equation Modeling (SEM), were adopted for data analysis. Findings of this objective reveal that the equipment management practices vary, to some extent, among different contractor sizes. While practices of medium and small contractors tend to be similar, practices of large contractors are different from those of smaller contractors. Large contractors often put more emphasis on outsourcing strategy for equipment management. They frequently dispose of or replace equipment as soon as the equipment becomes inefficient. Conversely, smaller contractors tend to mainly emphasize the company’s finances and budget availability for purchasing strategy, especially buying used machines. Overall, equipment practices of large contractors were found to be more successful than those of smaller contractors in minimizing equipment management problems. Among all equipment problems, downtime was found to be the most significant problem faced by highway contractors. The SEM model, constructed during the first objective, provides a framework for tracing the causes and consequences of downtime as well as recommends practices for downtime reduction. It suggests that contractors should place a strong emphasis on equipment maintenance as it has a significant influence on downtime and machine disposal practice. The model illustrates how the acquisition condition and operational practice of equipment affect downtime through a direct influence on maintenance quality. Improving machine operational practices could approximately create double positive effect on maintenance quality, comparing to the influence from improving the acquisition condition of equipment. The model also ranks equipment management practices according to their importance and effectiveness in reducing the downtime problem. vi For the second objective, data from ten contractor case studies (i.e. 5 large and 5 small to medium highway contractors) was collected and analyzed using System Dynamics (SD) methodology. The results show that, to overcome downtime problem, equipment management practices throughout a machine’s lifecycle must be viewed as an integration of multiple feedback processes, which are interrelated and interdependent with downtime. In reducing downtime as well as improving machine budget status, a variety of policies are recommended for implementation, including machine standardization, quality improvement team building, supplier strategy, and trade-in-for-new disposal. “Neutral or worse before better” results normally occur after the policy implementation due to delays in the improvement process. Such delay behavior was found to occur not only during the attempt to reduce downtime duration but also during the improvement process of machine budget status. As an additional research finding, the study also proposes a methodological approach for determining the timing for key equipment management decisions (i.e. major repair, overhaul, and disposal) through the application of simulations using actual equipment management practice data. Two simulators (one for large and one for small to medium contractors) were built based on the SD simulation models constructed to serve as tools for contractors to better manage their machinery effectively and efficiently since proactive actions can be triggered before such breakdown with costly downtime to occur during equipment operations. |
| Year | 2006 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Construction Engineering and Infrastructure Management (CM) |
| Chairperson(s) | Hadikusumo,B. H. W; |
| Examination Committee(s) | Ogunlane, Stephen. O.;H., T. Luong;Ndekugri, Issaka; |