Hello,
I am using PGSuper to confirm the deflection history of a 110' deck-bulb-tee girder.
The deflection graph shows a 2" downward deflection at 90 days, corresponding to the even "Erect Girders". The program defines this event as hauling the girders to the bridge site and removing any temporary strands (my girder has no temporary strands). My question is, what is causing this large downward deflection? I am assuming that during storage the bridge is already supported form the ends, so self-weight deflection should have already been accounted for. I don't understand how hauling could result in such large downward deflection.
Thanks!
BenV
Edit: PGSuper file attached. Relevant inputs:
110' nominal girder length
No cast in place deck
50 psf wearing surface (applied at 100 days)
| Attachment | Size |
|---|---|
 Victor Creek Bridge Girder Deflection History.pgs | 198.85 KB |
You are right, that doesn't make much sense. Please post your file and indicate which girder you are analyzing. I'm sure it's just an input thing.
I updated the main post with the file attachment. Analyzing Girder C at midspan. I have been checking and re-checking inputs and design criteria, but nothing seems to make a huge difference in the deflection graph. Please let me know if you spot any big errors!
The 2" downward deflection at time of erection is due to the girder self-weight and the change in support locations between hauling and erection.
The hauling conditions have the beam supported 14 ft from its ends. Once erected, the beam is supported about 1 ft from the ends.
I adjusted the storing, lifting, and transport conditions so that they match the final bearing configuration (1' from ends). The -2" deflection jump is still present at 90-days. With this setup, I would assume that the self-weight deflection should stay constant through storage and erection. Are there any other factors that might be influencing the beam at the 90-day event that I could double check?
If this 2" deflection drop was removed from the graph, it would match my hand calculations very closely.
I'm not sure what is going on with the deflection history graph. There appears to be some sort of erroneous datum adjustment at the time of erection. I'll mark this as a bug and get it fixed.
In the meantime, the Details Report and the Analysis Results graphs (both before and after erection) don't show that 2" change in deflection.
Thank you for the help!
I agree its most likely a glitch in the graph, because it doesn't show up in the final report.