Why are two similar bridges showing very different creep & shrinkage results?  Should we consider creep & shrinkage for substructure?

Question:
Creep and Shrinkage properties are set and linked to material C35/45. After analysis checking the result of tendon, creep & shrinkage secondary, 2 separate bridges showed huge differences. On the left, the result seems relatively high compared with the bridge on the right (the result is almost negligible).  Meanwhile, all other result seem to have a similar pattern. What's the reason for this difference?


Answer:
This is happening because of time-dependent material assigned to the substructure. Usually creep & shrinkage are only considered for the longitudinal direction of the bridge.  So, another material needs to be defined for the substructure and only the compressive strength behavior should be assigned to this material.
The creep and shrinkage secondary results are observed for both structures.


Creep and Shrinkage secondary forces occur due to the indeterminacy of the structure.

As in the left structure, 2 piers were used. Hence, the pier cap was producing the secondary moments for creep and shrinkage because of the indeterminacy caused by 2 piers. The only secondary moments are produced due to the portal frame effect.
While in the right structure, there is one pier, hence pier cap is determinate, and thus, secondary moments are not produced.
Creation date: 6/8/2021 1:59 PM      Updated: 5/10/2023 7:23 PM
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