# Analysis of BIM-Based Quantity Take-Off in Simplification of the Length of Processed Rebar
## 1 Introduction  
Rebar work is a representative labor-intensive construction project [1; 2; 3]. Moreover, it is very important work from the perspective of project cost management and process management, because it takes a lot of working hours on site [1]. Due to the nature of labor-intensive and field-intensive rebar work [1; 3], the increase in work efficiency can be greatly helpful to reduce overall construction costs. Rebar installation is commonly performed by a crew of experienced and skilled workers, who usually work in pairs [4], and it is time-consuming work [5]. Therefore, if the rebar itself is designed to be easily processed and installed in the field, the work efficiency of workers will be improved. In particular, if the number of rebar types handled in the field is reduced, repetitive work performance will be facilitated, increasing the work efficiency of workers. Therefore, these matters need to be considered in advance in the Quantity Take-Off (QTO) stage. QTO incurs a significant impact on the overall construction cost and construction period, as it supports estimation, cost management, and construction project planning [6; 7]. When automated through the implementation of BIM, QTO becomes an extremely useful task, which enables cost and schedule benefits by providing simple and accurate estimates for projects [8]. Meanwhile, substantial time and labor are wasted on distinguishing suitable rebars for use in rebar work in construction fields due to the diversity of rebar types, meaning that simplification of the rebar types can help to reduce this wasted time and labor. Due to the labor-intensive nature of rebar work, in which the labor cost accounts for 65% of theoverall cost, increased labor consumption directly impacts the project costs [1]. Thus, most construction projects in Korea perform simplification of the length types of processed rebar, and there are three common simplification methods: (1) simplifying the length to 100 mm units; (2) simplifying by rounding up to the smallest deviation among 300 mm, 500 mm, 700 mm, and 1000 mm; and (3) simplifying by rounding up to 500 mm and 1000 mm. The simplification methods of (1) and (2) are most commonly used, while method (3) is occasionally considered in the case of large-scale projects. Through this simplification method, it is possible to reduce the number of Length types of Processed Rebar Simplification (LPRS), which means the length types rounded up to a multiple of units (e.g., 300 mm, 600 mm, or 900 mm, etc.). Reducing the number LPRS affects rebar construction work productivity. [PERSON] et al. [9] and [PERSON] et al. [10] discussed the negative effects of variability in element size on the complexity of the configuration process. Furthermore, [PERSON] [4] illustrated that the increase in the number of member sizes of rebars undermines the continuity of the work and adversely affects efficiency. The research findings from previous work prove that the simplification of rebar size can lead to an improvement in work efficiency through a decrease in the number of rebar LPRS, thereby reducing working hours and labor costs. However, after cutting the simplified rebars into the actual lengths required, the amount that gets cut out is wasted. This can lead to a large loss of material costs because the accumulation of such wasted rebars can lead to an overall increase in material costs, as rebar work accounts for about 9.8% of the total construction costs [1]. Moreover, the price of rebar has more than doubled over the past 20 years [11]. In other words, the application of LPRS can increase the amount of wasted rebars due to the cutting process, leading to an increase in material cost, while increasing work efficiency and reducing labor. This means that it is important to find a proper level of simplification for considering labor cost and material cost together. Therefore, it is necessary to accurately analyze the effect of applying LPRS on the amount of rebar actually ordered.