## 4 Study of Optimal Evacuation Efficiency on Each Floor
### Evacuation Efficiency under Different Evacuation Plans  
To explore evacuation efficiency under different combinations of evacuation plans on each floor, this study conducted evacuation simulations for various scenarios. Since having individuals on the second floor take the elevator would reduce the number of elevator uses by individuals on other floors, decreasing the overall evacuation efficiency for the entire building, this study's plan involved having all individuals on the second floor evacuate via the staircase. By using the enumeration method, we listed 27 other different scenarios; additionally, we set up a control group with no restrictions on evacuation methods. The evacuation times under different scenarios are shown in Figure 2. In the table, \"L\", \"D\", and \"W\" represent the use of stairs, elevators, and unrestricted methods for evacuation on each floor, respectively. For example, \"2L3W4W5D\" means that this scenario involves individuals evacuating using stairs on the second floor, unrestricted methods on the third and fourth floors, and the elevator on the fifth floor. Based on the simulation results, curves depicting the variation of the shortest evacuation times, and evacuation times for scenarios closely matching the shortest time under various assistance ratios, are plotted, as shown in Figure 2. From the table, we can observe the following:  
1. For a five-story building evacuation, when the assistance ratio is less than 40%, the time variation curve for scenario C6: \"2L3W4D5L\" closely matches the curve for the shortest evacuation time. This alignment is especially evident at 0% and 20% assistance ratios, where the curves completely overlap, and at 10% and 30% assistance ratios, where the evacuation times are within 3% of the shortest time. Therefore, for a five-story building evacuation with an assistance ratio below 40%, C6 is recommended as the optimal scenario. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**The Type of Ground** & **Evacuees** & **Egress Width: b (mm)** & **Maximum Speed: v (m/s)** \\ \hline \multirow{3}{*}{level ground} & non-differently-abled individuals & 455 & 1.40 \\  & differently-abled individuals & 455 & 0.95 \\  & assistance groups & 900 \(\times\) 455 (length \(\times\) width) & 0.95 \\ \hline \multirow{3}{*}{staircase} & non-differently-abled individuals & 455 & 1.12 \\  & differently-abled individuals & 455 & 0.36 \\ \cline{1-1}  & assistance groups & 900 \(\times\) 455 (length \(\times\) width) & 0.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mixed individual evacuation parameters. 2. For a five-story building evacuation, when the assistance ratio is equal to or greater than 40%, the time variation curve for scenario C21: \"2L3L4W5L\" closely matches the curve for the shortest evacuation time. This alignment is particularly notable at 40%, 60%, 70%, 90%, and 100% assistance ratios, where the evacuation time is the shortest. Even at 50% and 80% assistance ratios, evacuation times are within 3% of the shortest time. Therefore, when the assistance ratio is equal to or greater than 40%, C21 is recommended as the optimal scenario. 3. From the shortest evacuation times for various assistance ratios in Figure 3, it is evident that, when the assistance ratio is less than 70%, increasing the assistance ratio does not significantly reduce the minimum evacuation time; however, once the assistance ratio exceeds 70%, assistance has a notable impact on the evacuation of differently-abled people. Therefore, in multi-story buildings where differently-abled people reside and evacuation is required, the self-evacuation capabilities of differently-abled people can be effectively utilized when the assistance ratio is less than 70%. Therefore, due to the conditions of differently-abled people, assistance is needed. In order to enhance overall evacuation efficiency, the ratio of assisting personnel should be greater than 70%. When the assistance ratio is 100%, the evacuation efficiency is the highest.