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Topic review (newest first)

4 Post by dpryl

You have mail.

3 Post by rabyaneh

Dear Sir,

Thanks for your response. I sent an e-mail description with a sketch to the following e-mail address:

cervenka@cervenka.cz

I copied my question below:


I am trying to model the release of the prestressing strands (cutting the strands so the force is transferred to the concrete) at one stage followed by the application of a concentrated load (shear test) at later stages.

The strands are released at f'ci (release strength of ~6.5 ksi). I used the Bigaj model to model the slip of strands at release. For the next stage, loading in shear, the concrete has developed its 28-day strength (13 ksi). At this stage, the bond model should be a function of the new concrete strength. The issue was that I could not specify variable material properties for the bond (as a function of the load stage).

For release, the girder is sitting on slabs and allowed to camber up (no support plates modeled). For the shear test, the girder is sitting on two elastomeric bearing pads and load is applied using a loading plate. (these support conditions are different from the support conditions at "release"; hence, I am using the construction process to add the bearing plates in).

I will send you a sketch as well.

Thank you,

Roya

2 Post by dpryl

Dear Roya,
it is not 100% clear to me what exactly you wish to model with the changing bond and construction process. Please send us some sketches illustrating the history to be modelled, and the material properties development (ageing or something else?).

By "release" you mean a complete removal/cutting/prestressing release, or prestressing losses due to creep+shrinkage, or something else/more?

1 Post by rabyaneh

Dear Sir,

I am modeling the release of a prestressed girder followed by a shear test, up to failure.
I am modeling an imperfect bond for the strands using the Bigaj bond model which is a function of the concrete strength. I have used the variable nonlinear cementitious material for the concrete material properties. I am interested in varying the bond capacity with this transition as well. I was wondering if you would have any recommendations regarding the bond model variation.
I thought of using construction stages and adding different strands with different bond properties after release. Please let me know what you think or if there is an alternative way.

Thanks for your time,

Roya