Is non-linear staged construction analysis necessary in stage post tensioning transfer girder???

[DavidStructural08]

I am just wondering if I need to do non-linear staged construction analysis in stage post tensioning transfer girder design. It seems to me that since stage post tensioning is performed, it will basically cancelled most, if not all, of the non-linear effects due to stage constrcution. The reason is that when you apply PT force to the transfer girder at the K-th phase, the PT force will reverse the deflection due to the load effect in the (K-1)-th phase.

It just seems to me that amplifying the load with copnsideration of the non-linear staged construction will be too conservative. Am I correct?

 

[rapt]

Not necessarily a non-linear analysis, but yopu will need to check for cracking at the various stages, both for downward load at the end of each stage (including construction loads and any extra loads that have been applied by then) and upward load at the start of the next stage. You also need to check ultimate capacity, shear etc at each stage to make sure you have sufficient ultimate capacity.

Remember if you are using bonded tendons, they will be unbonded at some point in the calculations until they are grouted.

 

[jorton]

The PT applied at the K-th phase will also reduce the PT effect of all previous stages - the analysis can get complicated quickly. I think a staged analysis is warranted.

What do you mean by non-linear? Staged analysis is non-linear since the structure changes, but this isn't what I typically think of as non-linear analysis. PT analysis is usually non-linear to account for time dependent effects. Time dependent effects must be accounted for in some manner.