Negative Moment in Pretension Girders?
1Q)
Why do the girders in this model (which should all be simply supported) show negative moment at the ends? They show zero moment at the ends when only dead load is applied, but when strength 1 load combination is displayed, they show significant negative moment at the supports.
Ans: In case of Strength 1 load combination, Tendon Prestress force is included, which is causing predominant Negative moments at the supports.
But as pretensioned beams are used in the model, there shouldn't be any negative moments generated at the supports. Underlying cause of this issue is in Definition of Transfer length. PFA the pretensioned tranfer length files, which explains the significance of transfer length in pretensioned girders. So we need to define the transfer length beforehand.
One more thing to note, Follow the attached pdfs to formulate load combinations for construction stage results.
2Q) Also, is it normal that the model should take 15+ minutes to analyze? Or does that imply a problem in the way it is constructed?
Ans: As your model includes Approximate estimate of time dependent tendon losses and moving load analysis. It would normally take a bit of time.
We can get the tendon losses directly from Results Tables> Tendon > Tendon loss
kindly reply back if you have any further issues.
Regards,
Why do the girders in this model (which should all be simply supported) show negative moment at the ends? They show zero moment at the ends when only dead load is applied, but when strength 1 load combination is displayed, they show significant negative moment at the supports.
Ans: In case of Strength 1 load combination, Tendon Prestress force is included, which is causing predominant Negative moments at the supports.
But as pretensioned beams are used in the model, there shouldn't be any negative moments generated at the supports. Underlying cause of this issue is in Definition of Transfer length. PFA the pretensioned tranfer length files, which explains the significance of transfer length in pretensioned girders. So we need to define the transfer length beforehand.
One more thing to note, Follow the attached pdfs to formulate load combinations for construction stage results.
2Q) Also, is it normal that the model should take 15+ minutes to analyze? Or does that imply a problem in the way it is constructed?
Ans: As your model includes Approximate estimate of time dependent tendon losses and moving load analysis. It would normally take a bit of time.
We can get the tendon losses directly from Results Tables> Tendon > Tendon loss
kindly reply back if you have any further issues.
Regards,
Pretension Tranfer length Check.zip
Vol.1_54_Why is dead load results of last construction stage not matching with dead load results in post cs.pdf
Vol.1_66_How to formulate load combinations for construction stage results.pdf
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