This test problem shows how construction stage analysis can be done for bridges that are simply supported for dead load and continuous for live load.

On this page:

Model Screenshot

Unable to render embedded object: File (Staged_construction_for_precast_girder_bridge.png) not found.

Approach 1 - Using Section Modifiers (Model B)

Key modeling steps

• Create 2-span precast girder concrete bridge from BrIM template, with double bearings at the interior pier.

• Manually define 15 continuity links connecting girders and deck of span 1 with girders and deck of span 2 at the interior pier.

• Create 3 groups to be used for the construction stage analysis for continuity links, deck and all other remaining objects.

• Use "Define > Named Property Sets > Area Modifiers" to define property modifiers for the deck shell elements to simulate the hardening of concrete.

• Set up construction stage analysis with separate stages to:
  • (1) add and load the girders
  • (2) add deck shell elements
  • (3) reduce the stiffness of the deck shell elements to simulate fresh concrete
  • (4) apply the deck dead load
  • (5) reset the stiffness of the deck shell elements to simulate hardened concrete
  • (6) add the continuity links to the model.

• Save results at the end of each stage.

• Define moving load analysis starting from the end of staged construction analysis.

Other Modeling Comments

• The bridge has fixed bearings (vertical, longitudinal and transverse translations fixed) at the bent and sliding bearings (only vertical and transverse translations fixed) at the abutments. However, it is required to add small stiffness for other bearing DOFs to stabilize the girder before the deck is erected. Otherwise stability problems may occur.

Results

• Check bridge forces/stresses for each step of the staged construction analysis → moments are as for a simply supported bridge.
• Check moments for the results of moving load analysis → moments are as for continuous girder.

Additional Screenshots

Moment at the end of staged construction (all loads applied to a simply supported model beams):

Unable to render embedded object: File (Moment_at_the_end_of_staged_construction_(simply_supported).png) not found.

Live load moments (live load is applied to continuous span):

Unable to render embedded object: File (Moment_for_live_load_(continuous).png) not found.

Approach 2 - Change Section Properties (Model C)

Key modeling steps

• Create 2-span precast girder concrete bridge from Quick Bridge template, with double bearings at the interior pier.

• Manually define 15 continuity links connecting girders and deck of span 1 with girders and deck of span 2 at the interior pier.

• Create 3 groups to be used for the construction stage analysis for continuity links, deck and all other remaining objects.

• Set up construction stage analysis with separate stages to:
  • (1) add and load the girders
  • (2) add deck shell elements
  • (3) reduce the stiffness of the deck shell elements to simulate fresh concrete
  • (4) apply the deck dead load
  • (5) reset the stiffness of the deck shell elements to simulate hardened concrete
  • (6) add the continuity links to the model.

Attachments

• [SAP2000 V12.0.2 file for model B|Staged construction for precast-girder bridges^SAP2000 V12.0.2 model B.zip] (Zipped SDB File)