The discrepancy in deformation results in the last construction stage and post-CS

Creation date: 1/30/2020 2:15 AM Updated: 5/20/2023 10:02 PM

Question: Why are the deformation results in the final and post-CS stages different?

Example:

Final stage Summation (CS) results

Post CS Summation (CS) results

Here's another angle on the same result

When I combine Summation (cs) with other load cases in the factored load combination for the AASHTO LRFD Strength 1 Load Combination, I get the following:

Answer:

Let us first try to understand why the deformation results look not as expected but when we check the stage/step displacement the results look as expected.

When we check stage 1 results only the girder are activated it is as expected:

But, when we check stage 2 results the plate nodes are activated in their original location and thus the deformation looks as shown below:

If we want to consider the deformation of girder 1 to affect the nodes which would be activated in stage 2, we need to check on the stage/step displacement and check the results.

Now, the discrepancy in deformations results in the last construction stage and post-CS is because we don't have the option of checking the stage/step real deformation option in post-CS. Usually, the forces are required for the design checks, and if that is checked between both cases, it would be the same as "stage/step real displacement", which only affects the deformation results and not member forces.

Hence, if we must check the design forces for the construction stage results and other factored load cases, the results would be as expected since the "stage/step real displacement" option doesn't affect member forces.

If we require the displacements check, then the "stage/step real displacement" from the construction stage and need to combine it with the other factored load cases, then we could extract this deformation from the table as shown below:

Now, these deformations are available in a table format which could be easily copy-pasted in excel for any further processing.

Wilson St 11-7-2019 Integral Abuts 55 Deg Expansion Case.mcb

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The discrepancy in deformation results in the last construction stage and post-CS

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