The approach is outlined for the development of an expert system for the -preliminary -design-of-bridges-(-RCAB£). using.lhe exp.ert system "shell, EXSYS, running under MS-DOS on an IBM-PC. After some consideration of the preliminary design process and the relevant design rules, the strategy for the development of the expert system is discussed. This was based on a series of knowledge sources integrated through a master knowledge source, with an exchange of data through a common data base. This approach, which fully uses the features of EXSYS, was found to be most satisfactory since each knowledge source could be tested and developed independently.