건축공사의 EVMS 활용을 위한 액티비티 적정 분할 방법

Abstract

It is the current trend that domestic construction projects are more focused on seeking methods to save costs within their budget rather than reasonable delivery shortening and cost saving through the process control. As the saving of input cost to the direct construction cost can cause quality degradation, however, it is necessary to employ cost saving techniques at the same time from a variety of aspects. As one of the methods to solve it, the Earned Value Management System (hereinafter referred to as the "EVMS") is recently coming to the fore. In this context, starting from July 1, 2000, the government institutionalized the implementation of more thorough construction management by applying the EVMS that compares and controls the "plan vs. achievement" of the cost and schedule for public construction works whose contract amount is 50 billion won or higher. But the present situation in the nation is that various data are not being analyzed for the institutional preparation and achievement assessment for the field application of the EVMS, and not even correct concepts have been grasped yet. This study, accordingly, surveyed cases of construction project and analyzed the actual status of their process schedules and progress control, divided the activities of the respective projects into the levels closest to the WBS(Work Breakdown Structure), a core element of the EVMS, and redrew up process control charts by assigning the cost resources of itemized statement to each work. This was compared with the process charts of existing cases and its deviation was analyzed to derive appropriate dividing criteria of activities. The results derived in this study are as follows: 1. When making a process control chart, activities should be classified suitably to the WBS integration criteria, and the processes with a high incoming ratio of material and equipment and outsourcing works should be divided into individual activities. In addition, in subdividing the activities of outsourcing works, it is adequate to estimate about 10-percent contract deposit of the relevant work as an already-progressed amount. 2. The SV and CV indicate the percentage of processes and construction cost to the control criteria line in the total construction cost, and hence, it is difficult to evaluate the profit and loss by a simple comparison in which the ratio of advance construction to future processes is included. It is therefore required to compare under-achievements and over-achievements to planned processes, not a simple deviation comparison in the control criteria line. The scheduled process chart and actual one in this study were analyzed by the absolute deviation with the control criteria point as "0" and the absolute deviation is defined as the summation of the absolute values of "unachieved rate of schedules" and "advance construction rate" 3. The absolute deviation in the existing process control chart occurred 47.80% on an average. It turned out that main processes of the deviation were reinforced concrete works, waterproof works and plastering works. In the case of the existing planned process charts, because the itemized statement system and the WBS are different, the cost and schedule are not interconnected, causing a lot of problems. Because activities in planned processes are not subdivided, adequate progress is not given to actually-peformed works and due to that, progress took place on over-achievement, causing problems such as under-achievement of progress and schedule delay. 4. The absolute deviation in the 180%-subdivided improved model within the suggested criteria line, compared with the existing activities which are 2.65% on an average. This demonstrates the absolute deviation decreased by 47.38% in the first, 35.42% in the second, and 57.96% in the third, which are by 46.92% on an average, in comparison with the existing planned process charts. This is because the existing activities were subdivided suitably to the WBS and thus previous/subsequent works with the control line as a reference were clearly differentiated, and accordingly the progresses were properly distributed. 5. The final construction cost estimated volume measured by management index of improved model scheduled process chart is 92.5% out of BCWS Accordingly, when applying improved model scheduled process chart, the whole construction cost will be 7.5% decreasing. As a result of having applied the method of subdividing the activities as describe above, the "plan vs. schedule" achievement rate increased and the absolute deviation to the unachieved rate and over-achieved rate decreased. It is therefore judged that the application of the EVMS by the subdivision method of activities proposed in this study would be appropriate.