# Airport pavement Maintenance Decision-Making System with Condition Cases Optimization
## 2 Airport Pavement Management System Architecture
### Decision Making Process for Airport Pavement Management System
#### 2.4.4 Sensitivity Analysis  
Sensitivity analysis was conducted by varying input variables for flexible pavement. For comparison, we included the results for do-nothing (DN) and network optimization (NO), which represent the application of the conventional network optimization. Analysis was performed using variables such as the minimum SL threshold, budget, analysis period, the lifespan extension effect after method application, and M&R cost, as shown in Table 3. For the minimum SL threshold, we examined cases with \(\pm 15\) points around the SL of 65 points, specifically considering thresholds of 50 and 80 points. Regarding the budget, we initially applied a value of USD 1000 and tested variations of \(\pm 10\%\) and \(\pm 20\%\). We expanded the analysis period from the initial 5 years, to 7 and 10 years. To calculate the change in the slope of the serviceability level (SL) performance curve after M&R, we divided the analysis into two cases: one where the overall lifespan was extended and another where the lifespan was extended for a specific number of years from the time of method application (Figure 4), where \(SL_{0}\) = SL score at the evaluation, \(m\) = original slope of SL performance curve, \(i\) = M&R method, \(t_{i}\) = time when M&R method \(i\) is applied, \(SL_{t,i}\) = SL score at \(t_{i}\), \(t_{end}\) = original time of end of life, \(t^{\prime}_{end,a}\) = time of end of life after applying method \(i\) (life after M&R method), \(t^{\prime}_{end,b}\) = time of end of life after applying method \(i\) (life extension method), \(m_{a}\) = slope of the SL performance curve after applying method \(i=\frac{threshold-SL_{t,i}}{t^{\prime}_{end,a}-t_{i}}\) (life after M&R method), and \(m_{b}\)= slope of the SL performance curve after applying method \(i=\frac{threshold-SL_{t,i}}{t^{\prime}_{end,b}-t_{end}}\) (life extension method). Figure 4: Comparison of life extension method (a), and life after M&R method (b). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variables** & **Negative** & **Original Value** & **Positive** \\ \hline SL threshold & 50 & 65 & 80 & \\ Initial Budget (USD) & 800 & 900 & 1000 & 1100 & 1200 \\ Analysis Period (year) & & 5 & 7 & 10 \\ Life Extension (\%) & \(-20\%\) & Refer Table 1 & & +20\% \\ M\&R Cost & \(-20\%\) & Refer Table 1 & +20\% \\ Definition of Life extension & Life after M\&R & Life Extension & \\  & method & method & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values for sensitivity analysis. Furthermore, we examined the results by varying the expected lifespan extension level after method application and the costs associated with each method by \(\pm 20\%\). The lifespan extension effect was increased or decreased by 20%, and this effect was also adjusted by the same ratio for second and third applications of the method. Table 4 shows the input data used for analysis, namely, five airports with different traffic volume, lambda value, and section conditions. The minimum value of SL was 40 and the maximum value was 100. Considering the experience, we distributed more than 70% of the sections with an SL score of 85 or higher. Sections for simulating rather deteriorated condition were scored in the range of 65 to 75. The analysis results are presented in Tables 5 and 6. Table 5 shows total B/C and final SL scores from original values. Differences in percentage among sensitivity analysis are also presented in Table 6. Total budget allocation showed significant variations in CCO's total B/C. When it decreased by 10%, there was approximately a halving effect, and when it decreased by 20%, it dropped sharply by 2%. When analyzing the two methods of lifespan extension effects, NO and CCO methods exhibited a more than twofold difference in total B/C, with no significant difference in SL after the analysis period (5 years). When extending the analysis period from 5 years, to 7 and 10 years, NO's total B/C increased, while CCO's B/C was higher than that for 5 years, particularly showing the highest value at the 7-year analysis period.