| Resumo: |
The construction companies are looking for new technological and management solutions to solve old problems related to the peculiarities of the sector. The high contingent of labor, low productivity and use of archaic techniques are some of many examples that can be pointed out. The introduction of new technologies increases the efficiency of construction systems while that make them more complex, requiring betters design, planning, execution and a more precise management of all these steps. Lean Construction is a production philosophy that meets the current demands, particularly to recognize the flow of processes and their negative interference caused by the problems and peculiarities of construction. One of the major challenges for the construction management is the execution of activities in accordance to the duration provided in schedule. Its common the occurrence of variability in this regard. Thus, the main objective of this research was to analyze the causes of variability in the execution time of the processes in different constructive systems. For this, a field study was realized involving nine construction sites of different constructive systems: reinforced concrete with masonry fence, structural masonry and concrete walls molded in site. The methodology was supported by others tools, with a questionnaire containing 31 causes of variability. For the analysis of the data, a Delay Factor was created and a methodology of risk level evaluation was used to identify and classify by gravity the variability causes. This analysis was done for each of the systems, as well as for the three hierarchical levels that participated in the interviews (engineers, foreman and workers). During the field study, best practices that reduce process variability were also identified. As the results, the constructive systems behaved differently on the major types of causes. The risk analysis and the Delay Factor showed a tendency for the (more industrialized) concrete wall system to be more susceptible to variability, but the impact of the delays is smoother than in the other two systems. The comparison of the hierarchical levels view of variability showed that, as the level increases, the recognition of the variability impacts on production is also increased. Also 21 best practices were raised in the construction sites that were linked to the reduction of 42% of the causes of variability. It was concluded that there is a deficiency by the part of the managers to deal with the impacts of the variability in the execution time of the processes. Despite industrialization efforts, many identified causes are well known in the sector, revealing a chronic problem of the construction environment. |
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