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• It may be useful to create and study a simplified model to gain insight into structural behavior. This includes creating a 2D model.

• Creating a 2D model composed of shell objects may then serve as a useful preliminary to the 3D model. A 2D model would represent a longitudinal section cut through the bridge and soil mass. This approach would reduce the model size and analysis time while providing the benefit of useful information and a comparison study.
  • Nonlinear layered-shell objects may be useful for 2D bridge models in which the arch or soil cannot carry tension.

• To most effectively model and mesh the 3D bridge structure, it may be best beneficial to use shell objects to draw the arch segments in the 2D elevation view, then extrude the shells into 3D solids using Edit > Extrude > Extrude Areas to Solids.

• To prevent tension from developing in the arch and along the soil-structure interface, gap (compression-only) link objects may be used to model support points.Nonlinear layered-shell objects may be useful for 2D bridge models in which the arch or soil cannot carry tension.

Arch system in 2D

To model an arch system in 2D, shell objects should be used for plane stress problems, and frame objects should be used for frame-type behavior. When using frame objects, a series of linear segments should be modeled to approximate the curvilinear profile of the arch.