CIVIL

Question:

Good morning.

Attached is the composite section post tensioned beam.

The cables 5,2,7 are stressed at factory when the beam is placed on the casting table.Therefore for first three stages i defined the vertical onedirectional springs.

From stage "day 14/instalation of beam"  i reduced the springs and defined the supports at end of beam only.

Is it the write solution for modeling a beam or there is other method ? Please have a look on my model.


In load case SW i defined the self weight of the beam by myself.the total load due to self weight is 88 ton.but in CS "14 day/installation of beam" the reaction due to dead load is 41+41=82 ton.

what is the reason please ?

regards



Answer:

Hello,

I understand the concern. 
Actually, this should not happen but this happening because the permanent support is coming onto the existing point spring which is deactivated. 
To avoid this what we can do is, there is 2 ways,
1) Don't provide the point spring support on the end nodes where the final supports are coming. This may give approximate result.

2) Make a node 10-50 mm inside at the ends and provide the point spring for last element there and activate the final supports at that node as shown below.







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Creation date: 6/8/2021 1:58 PM      Updated: 6/8/2021 1:58 PM
Files   
DataImage38.png
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DataImage82.png
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reaction due to self weight of beam.pdf
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Beam at axis 31- updated tendon stressing B5-A7-A2-B6-B4-A1-A3.mcb
205 KB