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Uncorrect results (deformations, forces) for prestressed beam elements

Question:

Hello all.
Attached is model of bridge using thenolgy of cantilever balanced method. For phase Etapa3-predpatie there suddenly strange deformations. Pls look at attached png images.
It seems that there is something strange with prestressing forces from tendon on the element.  n. 171
This element has composite section. Maybe this can cause the problems. But other elements with same section doesnt seem to have issue.


Answer:

Hello 
Greetings.

As option beam section changes with tendon is selected, what program does is, it remove the duct area from concrete section before the grouting stage to calculate the stiffness and after grouting, add the further equivalent stiffness of the tendons in the section. For details regarding that refer here.

Further, 2 types of error where received when I opened and ran the model.
1)  The first error was obtained when the midas was opened. This error is as follow.
To define the tapered section, we need to define two end section. But when two section imported from the SPC are used to form taper, the number of vertices in both the section should be same. So, this error could be possible reason for that as the number of vertices for both sections is not same. Please review the section used, especially property id section 8 and 9.


2) Second error is obtained from midas out file. 
This could be because the number of tendon used is high. Section stiffness is calculated as concrete area at that location - duct area. So, what could be that due to large number ducts presents, no concrete at that particular section is left and area might be becoming negative. We need to review the tendon placing and concrete area at place where ducts are placed. 
To prove this, tendon Top-01_11 and Top-01_12 are activated in V2_L6_predpatie stage but grouting of these tendons occured in next stage ( Etapa3_predpatie) where the abnormal behavior occurs. To check this, I deleted two tendons, then results obtained were fine.  


So, these could be possible reason. 
Either we can proceed by eliminating these error one by one or if tendon is not required for stiffness upgradation, we can keep the beam section property constant.
So, kindly check for these things and if issue still persists, kindly let me know.
Creation date: 5/31/2021 4:53 PM (jatin2010)      Updated: 5/31/2021 4:53 PM ()
Files   
203_most_skuska 2kable.mcb
2.4 MB
DataImage40.png
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DataImage40[1].png
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DataImage64.png
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Etapa3-pradpatie.png
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Summation.png
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