Abstract
The features of an expert system, developed for the pre-design of highway overpass R/C bridges, are presented and discussed. This system is implemented into a software and is aimed to facilitate the seismic upgrading of an overpass by isolating its deck with the inclusion of elastomeric bearings. The preliminary design of such an upgrade scheme is the target of this software based on the current design provisions of Eurocode 8 (Part 2) as well as on engineering decisions included in the expert system; it can also be extended easily to comply with alternative design provisions. The developed software is connected with a database of typically used steel laminated rubber bearings and relevant laboratory test results and it performs a series of checks according to Eurocode 8, in order to ensure the satisfactory seismic performance of the selected upgrade scheme. The parameters that are addressed within this software as independent variables are: the geometry of the overpass, the number of bearings at each deck support, the level of seismic action and the characteristics of the bearings (i.e. their geometry and shear modulus). The final selection of the bearing scheme (in terms of number of bearings and bearing dimensions at each support) is based on a costbenefit criterion aiming at optimizing structural performance at minimum cost. The methodology proposed for the preliminary design of seismically isolated overpasses and the software developed were validated through more rigorous dynamic analyses employing multi-degree of freedom numerical simulations of realistic bridge overpasses.