جستجوی مقالات مرتبط با کلیدواژه « Discrete event simulation » در نشریات گروه « عمران »

Optimizing productivity of construction has always been a challenge for project managers and planners. In previous studies, it has been pointed out that productivity is directly related to the number of workers unless the excessive number of workers in the workshop causes congestion. Discrete event simulation is one of the mathematical modeling methods used by researchers to study productivity in construction. Discrete event simulation models the operations considering the flow of resources and the state of entities within the system. In this model, the entities are passive elements that are processed during the work process. Due to the nature of the entities in a discrete event simulation model, it is not possible to investigate the effect of physical interaction of individuals on productivity using this method alone. Social Force Modeling has a great ability to model the movement of people and physical interaction between people and the environment. This study tries to investigate the direct impact of manpower on productivity by modeling the work process and the effect of physical interactions of workers due to the increase in the number of workers and workshop spatial constraints. For this purpose, a hybrid model has been developed that includes a combination of two models. In the first model, the discrete event simulation method is used to simulate the work process. In the second model, the movement and physical interaction of workers are modeled using the social force modeling method. The proposed hybrid model allows one or more activities to be simulated more accurately. The approach used in this paper is evaluated based on the data from a real project. The results clearly show the reduction in productivity due to overcrowding. The outputs of this work can be used to obtain the optimal number of workers in an activity. The model proposed in this paper gives project managers the chance to have more realistic simulations of work processes.

Realistic project planning is an essence for project success. Despite its simplicity, in such method, some metrics like schedule bottleneck points, work production and, resource utilization remains vague which in turn can lead to project cost and time overruns. Besides, since project stochastic scheduling is a kind of NP-hard problems, previous project planning literature suggests metaheuristics method and optimization algorithms like genetic algorithm and ant colony optimization algorithm. This study proposed using discrete event simulation for project stochastic scheduling as an innovative method, since: firstly, construction process has kind of discreteness identically resulting from different resourced interactions. Secondly, whole of construction project concepts can be modeled by discrete event simulation modeling elements and, thirdly, the logic of simulation models for each type of project would be same, i.e., it is required just to modify activities duration and the number of available resources. This study investigates a part of the total earth-moving operation of Dalaki dam as a case study. Having modeled the operations, it is observed that they used the best resource combination regarding project cost and time. Moreover, planning performance metrics such as schedule bottleneck points, various cycle productivity and resource utilization were calculated and discussed in depth.

The success of lean principles in manufacturing and the benefits arising from its use is one of the main motivations for adopting lean principles in construction .The lean construction strives for the same goals as lean production, namely to eliminate waste and to maximize value. One of the basic concepts in lean construction is called “perfection”, meaning that efforts made to decrease waste in every single phase of the projects has no limit and the enhancements resulted from implementation of lean principles must always be retained and improved. This paper pays attention to application of lean thinking in one of construction fields as a case study. Another aim could be mentioned as continuity of resulted enhancements caused by application of the theory by following perfection principle. To achieve and investigate the results, discrete event simulation for making activity under-study cycle model has been used. The case study in this research is foam concrete process in execution phase. The required data for building the simulation model has been collected using work and time study technique. Primary results show that different kinds of waste in a construction process can be reduced via adopting lean construction principles using computer simulation. The results obtained from applying lean principles demonstrate enhancement in performance of foam concrete cycle up to 15% and decrease in time up to 36%.