Prestressing Tendons

Question:

Hello,


I have a few questions about the prestressing tendons.


Lets say i have a prestressed bulb-tee beam bridge with 88 total strands (all straight) with several strands that have various lengths of debonding.

 

1. In the tendon properties window, when i click on the ... box beside Total tendon area and the window comes up with Strand diameter and number of strands, should these be entered for one strand (say 0.5" diameter, and 1); or should this be the strand diameter and the number of strands (say 0.5" diameter, and 88)?


2. I created the beams using the prestressed composite bridge wizard, where I inputted the strand pattern and debonding data, but I can't seem to be able to get to that information once the model has been created...is there a way to view or modify the strand patteren/debonding outside of the wizard?


3. How do I turn on/off the display of the strands in model view?


4. In the tendon prestress load window, when inputing the jacking stress value, should the value be entered for begin and end, or just begin?  Say i have a jacking stress of 202.5 ksi, should i enter that for begin and end or would that double the jacking stress?  (I watched a midas tutorial that entered the stress at begin and end, but saw in a midas pdf tutorial where it was only entered for begin, and end was zero.)


Thank you,





Answer:

Hello,

The response to each issue is as below:
1. In the tendon properties window, when i click on the ... box beside Total tendon area and the window comes up with Strand diameter and number of strands, should these be entered for one strand (say 0.5" diameter, and 1); or should this be the strand diameter and the number of strands (say 0.5" diameter, and 88)?
A:  Details of strand diameter and area should be entered only for a single strand here.

2. I created the beams using the prestressed composite bridge wizard, where I inputted the strand pattern and debonding data, but I can't seem to be able to get to that information once the model has been created...is there a way to view or modify the strand pattern/debonding outside of the wizard?
A:  To modify these data, just right click on any tendon profile and modify it.  The coordinates could be edited to change the debonding and strand pattern.

3. How do I turn on/off the display of the strands in model view?
A:  To turn of the tendon display, just right click on profile and prestress load and undisplay it as shown int he image below.

4. In the tendon prestress load window, when inputing the jacking stress value, should the value be entered for begin and end, or just begin?  Say i have a jacking stress of 202.5 ksi, should i enter that for begin and end or would that double the jacking stress?  (I watched a midas tutorial that entered the stress at begin and end, but saw in a midas pdf tutorial where it was only entered for begin, and end was zero.)
A:  This actually depends on jacking actually to be done.  Jacking at just begin would mean the tendon is anchored at other end and wouldn't be stressed from that end.  Jacking vales for both begin and end would mean that the strands would actually be jacked and stressed from both ends.

I hope that clarifies the doubts.  Kindly let us know if further assistance would be required.

Regards,
Nandeep
Technical Manager, MIDAS
Creation date: 10/17/2018 11:03 PM (dklee@midasit.com)      Updated: 10/18/2018 8:34 AM (dklee@midasit.com)
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