# Analysis of BIM-Based Quantity Take-Off in Simplification of the Length of Processed Rebar
## 4 Analysis & Discussion
### Discussion  
The results of the case study for five construction projects, which include 27 structures, are as follows. In the case of the beam member, when the length of processed rebar is not simplified (unrefined case), the average amount of rebar materials per unit area is 0.0110 t/m\({}^{2}\), and the deviation is 0.0116 t/m\({}^{2}\). For each case, the amounts of rebar increase for the simplified length of processed rebar are as follows:  
* Case A: average +0.62%, deviation 0.17%;
* Case B: average +1.09%, deviation 0.33%; and
* Case C: average +3.49% deviation 0.96%.  
In addition, the average number of LPRS per unit area of the unrefined case is 0.49 units/m\({}^{2}\), and the deviation is 0.33 units/m\({}^{2}\). The ratio of the number of rebar LPRS de-creased for each case is as follows:  
* Case A: average -25.54%, deviation 14.84%;
* Case B: average -37.79%, deviation 15.34%; and
* Case C: average -45.26%, deviation 14.80%.  
In case C, on average, the increasing rate in the amount of rebar compared to case A and case B was large, so if the decreasing rate of the number of LPRS was not significantly large, it was reasoned that selection should be avoided in terms of cost. In addition, the average value of the standard deviation of LPRS for the three cases is 14.99%, and there is no significant difference from each other, even though only 27 sets of data were used in this study. Therefore, even if the sample data are added for each case, it is considered that the LPRS-related result values will not change significantly.  
In this study, the slabs were divided into regular and irregular according to shape. When the length of processed rebar was simplified, reducing the number of LPRS for irregular slabs is more efficient as compared to regular slabs (cases A, B, and C for irregular slabs were reduced by 18.5%p, 16.7%p, and 14.3%p more than regular, respectively).  
The existing studies have limitations in that work efficiency or LPRS were not considered together with minimizing the waste of rebar, and almost all of them were difficult to apply to the factory processing method. On the other hand, in this study, a more practical analysis was conducted by simultaneously considering the simplification of the length of rebar related to work efficiency and the amount of rebar materials that fluctuated accordingly. The results of this study are expected to contribute to preventing material costs from increasing excessively by quantitatively analyzing the impact level of simplification on the amount of rebar materials and LPRS. In particular, it is considered that it can be useful for construction projects, to which the factory processing method of rebars is applied.  
Even though the analysis on the simplification of the length of rebar was conducted in this study, it cannot be said that optimization was performed. For instance, the work efficiency that fluctuated according to the number of LPRS can be converted into labor costs. Similarly, the quantity of rebar materials can be converted into material costs. Likewise, both costs of this inverse relationship are integrated in terms of cost and can be used to derive an optimal simulation of the length of rebars. Therefore, in future studies, the optimization of simplifying the rebar length will be conducted to minimize overall construction costs.