# Knowledge-Based Fuzzy Expert System to the Condition Assessment of Historic Road Bridges
## 4 Conclusions  
Given the complexity of the overall problems of assessing the condition of historic road bridges, a systematic analysis was performed, which resulted in the development of an expert system. The proposed model is a tool to improve and enhance the assessment of historic road bridges. The implementation of the expert system, using the proposed methodology, enables the involvement of all relevant experts in the assessment process and provides a precise and objective assessment of the condition of historic road bridges. For the model of the condition assessment of a historic road bridge, a fuzzy logic procedure was used, more precisely an FWGM approach based on obtaining a bridge rating using a fuzzy geometric mean and the centroid method. For the purpose of this model, data of each bridge were collected based on the visual expert assessment of the bridge elements. Thus, the component ratings (superstructure, substructure, and equipment) were obtained, which were then assigned relative importance using the AHP method, and the sum of the weighted component ratings gave the final bridge rating expressed as the HRBCAI value. This way, the assumption was proved that the newly formed expert system, with the collected adequate data and knowledge, provides outputs of the historic road bridges that the expert himself made. It has been proved that the results of the expert system are quite similar to the expert's assessments, and the formation of the system is not only practicable but also suitable. A computer algorithm has been developed based on the proposed methodology for condition assessment through the rating of the bridges. From the obtained results it can \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Bridge Label** & **Name of the Bridge** & **HRBCAI** & **Expert** \\ \hline B1 & Jovica bridge & 73.602 & 75 \\ \hline B2 & Bridge over the river Matica & 38.594 & 40 \\ \hline B3 & Bridge in Rastoke & 60.532 & 60 \\ \hline B4 & Bridge Brvina on the river Vrljika & 91.249 & 95 \\ \hline B5 & Bridge on Bublin on the river Vrljika & 77.641 & 80 \\ \hline B6 & Zmijavacki bridge on the river Vrljika & 80.131 & 80 \\ \hline B7 & Bridge on the stream Suvaja/Karalipeov bridge & 80.310 & 80 \\ \hline B8 & Bridge Sumet over the channel Jaruga & 71.199 & 70 \\ \hline B9 & Bridge Jasenovac on the river Jaruga & 86.621 & 90 \\ \hline B10 & Bridge on the river Jaruga nearby Mračaj in & 72.240 & 75 \\ \hline B11 & Bridge at the quarry “Lavécvić & 80.917 & 80 \\ \hline B12 & Zrnovacki bridge & 89.254 & 90 \\ \hline B13 & Bridge over the river Jadro & 88.035 & 90 \\ \hline B14 & Bridge at the entrance to the factory “Majdan” & 79.176 & 80 \\ \hline B15 & Rera/Vetmin bridge & 73.871 & 75 \\ \hline B16 & Bridge on the river Grab & 78.817 & 80 \\ \hline B17 & Bridge on the river Kosinac & 87.833 & 90 \\ \hline B18 & Bridge Blato on the river Cetina & 59.649 & 60 \\ \hline B19 & Pavča bridge & 98.167 & 100 \\ \hline B20 & Bridge on Panj & 98.166 & 100 \\ \hline B21 & Baleki bridge & 98.184 & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Historic Road Bridge Condition Assessment Index (HRBCAI) values for historic road bridges values obtained by the proposed model and their comparison with the values given by the expert. be concluded that the methodology can handle a various number of bridges with all considered components, elements, and scales of rating. Thus, the proposed methodology would surely help the structural engineering experts and decision-makers concerned with the management of bridges to achieve a systematic and suitable judgment and to design a methodical approach for the recovery, rehabilitation, or demolition of the bridge in future years. Until now, no systematic approach has been developed for historic road bridges conditions assessment that includes a detailed evaluation of its elements throughout combinations of \(\alpha\)-cut sets.