*5.3. Model Validation*

The amount of processed rebar and the amount of loss from cutting and bending, as shown in Figures 7 and 8, rise over time. As a result, the individual phases in the processing of rebar can be reflected in the suggested simulation model.

#### **Figure 7.** Model validation: D10 rebar time plot.

#### **Figure 8.** Model validation: D13 rebar time plot.

For the considered plant, the total number of working hours per day is 11.5 over weekdays, with 200 t of rebars processed per day according to the machine capacities. If the simulation model is run for 11.5 h, and 200 t of rebars are machined, the simulation model can be considered valid. The simulation results indicate that 202,856 kg, that is, approximately 203 t of rebar, is machined in 11.5 h. The results are shown as Table 6. Therefore, the optimal production plan and simulation model can be considered valid.


**Table 6.** Results of simulation validation.

#### **6. Conclusions**

This paper proposes a DES model to identify the optimal combinations to decrease the loss rate and promote rebar fabrication to achieve simultaneous delivery to multiple projects. The optimal fabrication plan to minimize the loss rate was formulated based on the collected data. By setting up the rebar type and machine features that affect the loss rate and time needed for rebar fabrication as parameters, the simulation model was proven to be accurate.

Human aspects were not taken into account because the model's variables only included raw steel and machine characteristics. Consequently, the results obtained using the simulation model may be different from the loss rate of the actual rebar fabrication plant. Nevertheless, this study makes several valuable contributions. First, the suggested model may take into account the machine specifications for each piece of machinery that affects the processing speed and loss rate. By adjusting the parameter values to acquire the optimization results, the suggested model may, thus, be simply applied to any plant. Second, the manager's experience or intuition are often used to manage the loss rate. The suggested model can assist in creating an objective plan for the fabrication of rebar. Because it can

reduce the percentage of material prices in construction projects, the decreased loss rate has a substantial economic impact. In future work, the proposed model can be extended to more diverse cases to optimize project costs in the construction industry.

**Author Contributions:** Conceptualization, E.H., J.-S.Y., M.H. and Y.J.; Formal analysis, E.H., J.-S.Y. and M.H.; Funding acquisition, J.-S.Y.; Investigation, E.H., M.H. and Y.J.; Methodology, J.-S.Y., J.S. and M.H.; Project administration, J.-S.Y. and J.S.; Resources, J.-S.Y.; Software, M.H.; Supervision, J.-S.Y. and J.S.; Validation, J.-S.Y., J.S. and M.H.; Visualization, E.H. and M.H.; Writing—original draft, E.H. and Y.J.; Writing—review & editing, J.-S.Y. and J.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Korea Agency for Infrastructure Technology Advancement (KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (Grant 22ORPS-B158109-03).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**

