| Abstract: |
Improving Productivity of Repetitive Construction Operations Using Simulation ModelsProductivity is an index that measures outputs (good and services) relative to the input (labor, materials, and other resources) used to produce them. It is a measure of the effective use of resources. Numerous factors affect productivity. Among them are methods, capital, quality, technology, and management. Consequently, it is best to treat productivity as approximate indicators rather than precise measurements. Productivity measures allow managers to judge performance, and decide where improvements are needed. A number of modeling tools have been specially developed or proposed to measure and improve productivity for the construction management area (Stevenson, 1996).The construction field operations are classified by Halpin and Riggs, 1992 into four levels, each more detailed or refined than its predecessor (Organizational, Project and activity, operation and process, and work task). Construction equipment was classified into four categories: tools, power tools, automatic tools, and robots, based on the distribution of physical components and information components between man and machine (Everett and Slocum, 1994). The selected cases of study cover the first three levels of Everett classification, and the third level of work according to Halpin hierarchical, these operations are tunnelling (TBM), microtunnelling (pipe jacking), mechanical plastering, and manual plastering.Simulation technique proves its capability of assessing productivity of any construction operation that has repetitive nature. In this study, MicroCYCLONE version 2.7 is used to analyze selected cases studies construction processes and predict production rate. In construction the reason for modeling and simulating a production system is to examine the interaction between flow units, determine the idleness of productive resources, locate bottlenecks, and estimate the production of the system as it is designed. Construction operations range from manual to mechanical, these operations are difficult to analyze and optimize using standard mathematical methods. Simulation is an alternative method of analysis that offers numerous benefits. Simulation technique proves its capability of assessing productivity of any construction operation that has repetitive nature. To design construction operations it is necessary to make decisions, these decisions include determining crew size, selecting equipment, establishing operating logic, and selecting construction method. The application of simulation technique requires several steps: select the simulation engine (program) that can be used, design the operation simulation model based on the selected simulation engine, prepare the operations activities duration, simulate the designed model, simulation results validation, and analyze the simulation results to assess productivity. MicroCYCLONE production by cycle report shows the production in units per hour per cycle. This report presents the cycle number, the simulation time when that cycle was completed, and the cumulative productivity at that time. The number of cycle can be changed until reaching the steady-state phase.Simulation is often used to evaluate and compare the different construction methods according to some objectives to select the best one, which meet needs required. For such comparison to be valid, it is important to compare the alternative at the same conditions so that none is favored more than the others. To compare the operation alternatives, it is necessary to structure simulation models so that chance impacts all alternative in a similar manner. This is easily accomplished by using MicroCYCLONE as simulation engine to perform a meaningful comparison of construction alternatives. It is important to design the true model and validate it.The basic objective of this research is to study the effect of applying simulation in productivity improvements at various construction operations ranges from manual to mechanical operations. When the operation nears to automation, the productivity improvement is decreased because the control resource is the equipment as in manufacturing. In manual operation, the tools and human are the main resources and can be easily resized and redesigned with minimum cost increase. So a productivity improvement is high in manual operations. Productivity improvement percentage for TBM, microtunnelling, mechanical plastering, and manual plastering operations are 2.3, 17.5, 22.4,and 35.6 consequently. If we let T = (actual cycle duration) – (best cycle duration), then the comparison between models designed depends on T. The saved time in constructing the tunneling and plastering operations is shown in Figure 1 below, the area under each curve present the saved time for each case study. It’s noticed that the area under manual plastering operation is the largest one and decreased until reaching the area under the TBM operation. The time saved, and productivity improvement after applying simulation is proportional diversely with applying machines in construction operation.
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