Case-Based Approach for Steel Bridge Fabrication Errors

Abstract

A rule-based system for resolving fabrication errors in steel highway bridges, the Bridge Fabrication Error Solution Expert System (BFX), is in operation at the Kansas Department of Transportation. The set of more than 100 cases gathered for development of BFX provided an opportunity to explore a case-based approach to solutions in this domain and to compare the caseand rule-based approaches. The case-based system CB-BFX (case-based-BFX) was created using the programming language CommonLISP and the case-based reasoning tool MEM-1. CB-BFX was evaluated by comparing the cases in the case-base among themselves as well as by paralleling the evaluation procedures used for BFX. A method of measuring internal consistency was developed based on the level of symmetry in case matching. Using a case-based approach alone provides engineering guidance in 82% of the cases, a substantial improvement over the rule-based performance of 63%. Using a combined approach of the rule base and case base gives an overall success rate of 91%. The case-based system is also easier to expand.