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Steel Tub Girder - Additional Bearing Construction and Deconstruction

Follow the steps below to construct and deconstruct temporary bearings on a steel tub-girder model.

This article walks through adding temporary bearings on the steel tub-girder model shown below. Two extra supports are added at the 25 ft and 75 ft stations of the 100 ft girder. The construction is staged in three steps.

image-20250513-153553.png

  1. Create the additional support lines.

  2. Create additional insertion points on the new support lines. The insertion points could also be added to existing support lines using a longitudinal offset, but a new support line is usually easier to manage.

  3. Include the new insertion points in the girder layout. The girder is configured to generate bearings on the same support lines as the insertion points listed in its layout.

  4. In the tub girder's FEA Setting tab, select all bearing insertion points related to the girder in the Support input. The insertion points marked with the blue arrow in the screenshot are the additional bearings.

  5. Define bearing fixity for the new insertion points.

  6. Construct the bearings stage by stage under Bearing Construction.

  7. Select the additional bearings to be removed under Bearing Deconstruction.

Animation of the resulting deformation across construction stages:

Final deformed shape after all stages:

Place additional insertion points so they coincide with web nodes, or add an internal diaphragm at the same station. An internal diaphragm is a transverse stiffener inside the tub that ties the two webs together; without it, the local stiffness at a midspan support is low and you may see exaggerated deformations at that station.

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