Abstract
The increasing number of prefabrication projects has increased the demand for precast concrete (PC) components. The production cost of PC components significantly affects the development of the precast industry and the progress of prefabrication projects. To reduce the production cost, both the delivery delay time and component storage time must be reduced. Flow-arrangement optimization is generally performed using the genetic algorithm. However, this method cannot always yield a perfect optimal solution. Moreover, the traditional optimization model does not consider the impact of the overtime hours of workers on the project costs. In this study, a mixed-integer linear programming (MILP) model was developed to optimize the production scheduling by minimizing the storage and delay times. The total delay time for the components was reduced by 55.3%, from 3.8 to 1.7 h, and the total storage time for finished components was reduced by 20.3%, from 6.4 to 5.1 h. Then, the use of the MILP model was extended to optimize the production scheduling by minimizing overtime. Finally, the feasibility and effectiveness of MILP were verified by comparing the results. The total overtime decreased by approximately 24.5%, from 11.5 to 9.3 h. It has been demonstrated that the proposed MILP model can achieve a better production sequence with less overtime. The findings of this research can be deployed in optimizing efficiency in the real-life scheduling of production sequence.
Highlights
Because of the drawbacks of conventional on-site construction approaches, the construction sector consumes approximately 40% of the total global energy, uses 40% of the global materials, and produces 50% of the global waste [1]
A primary difficulty in precast concrete (PC) production is how to manage PC completion times and delivery times across the assembly line when the orders received by the factory are approaching the work limit load. e overdue delivery of PC causes serious problems, such as degraded component quality, higher labor costs, rescheduling of construction activities, and project delays. erefore, delivering the components to the construction site on time is critical to ensure the smooth construction of the prefabrication project. e delay time caused by the prefabricated component manufacturer is the Advances in Civil Engineering most common situation in prefabrication projects
I where I represents the total number of components required as per the order, i represents the production order of the component, ETiand TTi represent the storage time and postponement time of component i, respectively, αi and βi represent the weights of the storage time and delay time of component i, respectively, and αi × ETi and βi × TTi represent the weighted penalty of the storage time and delay time of component i, respectively
Summary
Because of the drawbacks of conventional on-site construction approaches, the construction sector consumes approximately 40% of the total global energy, uses 40% of the global materials, and produces 50% of the global waste [1]. E overdue delivery of PC causes serious problems, such as degraded component quality, higher labor costs, rescheduling of construction activities, and project delays. E aim of some studies [7, 11, 12] was to minimize the delay time and optimize the scheduling scheme using the genetic algorithm (GA). Owing to the characteristics of the GA, the optimization results obtained are not necessarily the optimal solution Another straightforward criterion is the minimization of machine idle time to increase machine utilization or productivity [13]. Compared with the FSSM, the MILP model can obtain a better schedule of prefabricated component production with less penalty cost. It was demonstrated that the model can effectively optimize the production sequence of components to reduce the overtime cost
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