Seismosoft | Earthquake Engineering Solutions

I wish to ask as frp-confined concrete model is used to simulate the frp wrapping effect on concrete, should this material model be assigned to the core or cover part of the RC section. If it's to be assigned for the cover part of the RC section only, then should the confinement of the core part be enhanced through increasing the confinement factor, or that would be accounted automatically by the software.
Thanks,

Hi qalchatti,
The answer to your question depends a lot on what you want the FRP for. If you're just interested in providing your section with additional confinement, I would say you should increase by yourself the confinement factor of the core section.
On the other hand, if you want to use the FRP to increase the flexural strength of your element, then I think you should do as you're mentioning, i.e., placing the material in the unconfined part.
Be aware that if you are trying to model the FRP jacketing of your element without proper anchorage at the bottom, you should not include the material along the whole element, because the program will consider increased flexural strength.
Regards,
Ricardo

Hi,
where the thickness of the FRP is included? and how i can to model a beam with frp on 3 sides(bottom side and left and right sides for a part of the hight)?
if the answer is in past posts, can you show me it with a link?
thanks

Dear paky983,

Have you not tried using the 'search' link of this forum, using "FRP" as keyword? If you do, you will find a number of posts discussing the modelling of flexural retrofitting with external frp (or steel) layers.

Seismosoft Support

hi seismosoft support,
thanks for the answer. I have read the forum and i understood that there are two ways to modelling structures with frp.
1)the model con-frp to be using the existing sections for concrete cover and section core.
2)using a new cross-section to add to existing sections with
a material model featuring the properties of the retrofitting material.

Is it all correct?

Now,about this two ways i have any question:
1)In the first way,the thickness of frp is included in the "FRP jacket ratio"?
2)In the second way, what material should I choose in seismostruct between the existing ones, for the retrofitting material?maybe the trilinear FRP model?

Thanks for your precious support.

Hi paky983,

You are right. You can opt for one of the those options.
Answering to your questions:
1) The 'FRP jacket ratio' is the ratio between the FRP and the concrete areas, so knowing the FRP thickness and the section dimensions you can easily set this parameter;
2) Sure, you can employ the trilinear FRP model

Cheers,

Federica

Thanks very much Federica,

so... i have had convergence problems about portal2d... analyzing a portal3d,instead, i obtained results expected .
I noted that the two ways have differents results .
The first, with using con_frp, it's better about the increase of only displacements, while the use of a new additional section increase the force too.
I'm doing something wrong?

After the portal3D, I have analyzed my structure of thesis (pushover analisis) and i have a recurrent error. In the "Permanent Loading" phase appears written:
"LF= 0.00000,LF_incr= (Iter: 1 => fbd_Inv)... Unable to apply the entire permanent load. Analysis terminated".

I'm changing the parameters of convergence but no solution.

Pushover analysis converge in the initial structure.
Now i have added only a rectangular hollow section in the terminal part of the pillars to reproduce the frp-effect and running the analisys I get the error mentioned above.

I send you my input file ("pushY_frp")
Regards,
Pasqualino

quote:Originally posted by fbianchi

Hi paky983,

You are right. You can opt for one of the those options.
Answering to your questions:
1) The 'FRP jacket ratio' is the ratio between the FRP and the concrete areas, so knowing the FRP thickness and the section dimensions you can easily set this parameter;
2) Sure, you can employ the trilinear FRP model

Cheers,

Federica


Hi,

I have a question which might not be so appropriate, but it's a concern for me. For considering the FRP thickness in the con_frp model should the NOMINAL THICKNESS of the FRP sheet or ACTUAL CURED THICKNESS of the FRP sheet be used?

For instance, my FRP's nominal thickness is 0.0065 in/ply (0.165 mm/ply), while the actual cured thickness of the same single ply laminate (fibers+resin) is 0.02 to 0.04 in (0.6 to 1 mm).

It was a concern for me since the plasticity of the FRP's come from the resin part, saturating fibers. That's why, had this question in mind since it ends up in different FRP JACKET RATIOS. Thus NOMINAL FRP's THICKNESS or CURED FRP'S THICKNESS?

Sincerely,
Mos

Dear Mos,

We would suspect that what you call "cured thickness" is the one to be considered, but, as usual, the best way of resolving this type of doubts is for you to model an experimental test and compare the results obtained with the different modelling assumptions.

Seismosoft Support