Section Stiffness Scale Factor

Question:

Dear MIDAS,

I am concerned that the Section Stiffness Scale Factor is not working correctly with construction staging in MIDAS 2018. The attached model of a simple fixed beam has a section stiffness scale factor activated in the second step for the end elements at the supports. The section stiffness scale factor has a value of Iyy = 0.001, and is equal to 1.00 for all other DOF. However, the moment diagram does not change in the step during which the scale factor is activated. In the third step of the model, hinges are activated at the ends of the beam, and the moment diagram changes to a simply-supported condition as it should. Shouldn't the moment diagram at the end of the second step be essentially the same as at the end of the third step? I have attached the model file.

Thank you,


Answer:

Hello,

Actually this difference is in how section stiffness scale factor and beam end release are considered.
For section stiffness scale factor, it is assumed that applied load is leading to reduction in stiffness and this is not redistributed.  However, if any new load is applied, then for that new load, this will behave as a section with reduced property.  Hence, for new load, this would act as simply supported.
However, when beam end release is provided, the forces due to the already applied load are also redistributed, making the overall behavior as simply supported.
To make the above clear, I've modified the sent model.  Kindly check the results of first step of each construction stage.  Also, with same setting check result of just current step as well.  It'll clarify on how this command is being applied.
Kindly let us know if further assistance would be required.

Regards,
Nandeep
Technical Manager, MIDAS
Creation date: 10/17/2018 9:07 PM (dklee@midasit.com)      Updated: 10/18/2018 6:38 AM (dklee@midasit.com)
Files   
DataImage67.png
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Stiffness Reduction Test.mcb
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Stiffness Reduction Test.mcb
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