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A generalized, three-dimensional, finite element bridge model was created in order to efficiently and accurately assess live-load girder distribution factors for a variety of bridge types. This model shortens the time required by bridge analysts to develop individual finite element models for bridges of varying geometries. The creation of the generalized bridge model was based on previous modeling techniques successfully implemented and tested by different researchers. The proposed modeling scheme utilizes a combination of shell elements for the deck, frame elements for the girders, and rigid beam links connecting these two element types. The versatility of the finite element program, OpenSees, allowed for the creation of this generalized bridge model. The Tcl scripting language, used to define the analysis for implementation in OpenSees, enhances the capabilities of generalizing the truck types and loading procedures for analysis.
The generalized finite element bridge model developed for use in OpenSees was validated through comparison to two bridges analyzed by field testing and finite element modeling in a previous research study. The girder distribution factors of these conventionally reinforced concrete bridges were determined with the generalized bridge model and compared to the results of the previous research and to factors determined with the AASHTO LRFD (2003) specification. The results determined with the generalized model compared well with the results of the previous study and effectively validated the model. Factors evaluated with AASHTO LRFD (2003) were shown to be generally conservative. The generalized bridge model was found to accurately and efficiently evaluate live-load girder distribution factors and could prove useful to economically rate a large number of bridges. |
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