FRP Confiend Concete on SeismoStruct Ver-7

[anantparghi]

Hi there,
How do I model FRP confined circular RC column. Should I use the Material Type :Frp_tl?
For the section, should I select a composite circular section? or Reinforced Concrete Circular Section?

For the confinement factor: there is an Option to provide the FRP materiel properties:

FRP jacket, 1)Jacket thickness, 2)FRP elastic Modulus and 3)Jacket strain.

I was just wondering that the above strain is for FRP coupon's ultimate stain or the FRP-Confined concrete cylinder's ultimate strain?
I use the RC circular section, and provided the FRP jacket material properties 1)Jacket thickness, 2)FRP elastic Modulus and 3)Jacket strain. But, I am getting same results like without FRP and with FRP.
If anybody could help, I would greatly appreciate you.
Thanks

[z.gronti]

In SeismoStruct v7.0 you may insert a Reinforced Concrete Circular Section and provide the FRP material properties in the confinement factor calculation module. Of course there is still available the choice of using the frp_tl material type. The quantities that should be assigned in the confinement factor calculation module are about the FRP's properties. Once you assign the FRP's properties the confinement factor should change, unless the defined jacket thickness isn't enough to increase the confinement factor value.
A search in the forum might also help you, as well as the following topic:
http://seismosoft.com/forum/topic.asp?T ... hTerms=FRP

[fakharifar.mostafa]

As stated by z.gronti, using the Confinement Factor confinement factor is the preferred option, by simply using FRP jacket.

As long as getting same results, what is the analysis you are carrying out. If it is simply eigen value analysis, no surprise you get similar results. Also, if your original column (no FRP jacket) has a confining factor similar to FRP-confined column, again you should almost get similar results (equal confinement factor = equal confining pressure provided = similar confined concrete stress-strain curve). Modern RC columns constitute comparable confining pressure to substandard FRP retrofitted columns.
What I stated here applies only to FRP-confined column with unidirectional fibers perpendicular to column axis.

If your confining repair jacket constitutes bidirectional fibers, or FRP anchors, then you need to use a composite circular cross section and assign frp_tl material for the jacket to include the effect of longitudinal fibers. However, this is not an advised method, unless you exactly know what is going on, as it is tricky. The discussion below may help you on this matter too. Good luck.

http://www.seismosoft.com/forum/topic.a ... =interface

[anantparghi]

Hi there,
Thank you very much for your reply and advise sir, I appreciate you.

I am modeling a Reinforced concrete column; as built column and strengthens with CFRP composites. I am doing Static time-history analysis.I use the following properties and section.

Material name: Concrete (Con_ma)
Longitudinal steel rebar: stl_mp
Lateral steel rebar: stl_mp
Section: Reinforced concrete circular section (RCCS).
As built column confinement factor: 1.067
CFRP strengthens column: FRP jacket thickness 0.11mm, FRP elastic modulus (266 GPa) and jacket stain (0.0163), the confinement factor: comes our 3.4854 for CFRP composites.

Element class:inelastic displacement-based frame element (infrmDB), section fibers-200.

I was wondering that, if the confinement factor of as built column (1.067), and the confinement factor of CFRP strengthen column (3.4548) different, then why the analysis results are same, he stiffness and displacement both are same for as built and CFRP strengthened column.
If anybody, could please help me to understand the topic.
Thanks


Hi there,
How do I model FRP confined circular RC column. Should I use the Material Type :Frp_tl?
For the section, should I select a composite circular section? or Reinforced Concrete Circular Section?

For the confinement factor: there is an Option to provide the FRP materiel properties:

FRP jacket, 1)Jacket thickness, 2)FRP elastic Modulus and 3)Jacket strain.

I was just wondering that the above strain is for FRP coupon's ultimate stain or the FTP-Confined concrete cylinder's ultimate strain?
I use the RC circular section, and provided the FRP jacket material properties 1)Jacket thickness, 2)FRP elastic Modulus and 3)Jacket strain. But, I am getting same results like without FRP and with FRP.
If anybody could help, I would greatly appreciate you.
Thanks

[z.gronti]

The reason why you get a confinement factor equal to 3.4854 is that you probably have inserted the value for the jacket thickness in the confinement factor calculation module in mm, whether it should be assigned in m.
The confinement (modeled only through the confinement factor) affects the maximum stress, the strain at the maximum stress and the descending branch of the material model. It only marginally affects the initial stiffness. The analysis results you get depend on the type of the analysis and loading , as well as the structure you have.

[fakharifar.mostafa]

quote:Originally posted by anantparghi

Hi there,
How do I model FRP confined circular RC column. Should I use the Material Type :Frp_tl?
For the section, should I select a composite circular section? or Reinforced Concrete Circular Section?

For the confinement factor: there is an Option to provide the FRP materiel properties:

FRP jacket, 1)Jacket thickness, 2)FRP elastic Modulus and 3)Jacket strain.

I was just wondering that the above strain is for FRP coupon's ultimate stain or the FRP-Confined concrete cylinder's ultimate strain?
I use the RC circular section, and provided the FRP jacket material properties 1)Jacket thickness, 2)FRP elastic Modulus and 3)Jacket strain. But, I am getting same results like without FRP and with FRP.
If anybody could help, I would greatly appreciate you.
Thanks



Sorry I forgot to answer. You can find your answer regarding the ultimate strain of FRP in the below paper.

Wu, Y. F., & Jiang, J. F. (2013). Effective strain of FRP for confined circular concrete columns. Composite Structures, 95, 479-491.

[anantparghi]

I am modeling a Reinforced concrete column; as built column and strengthens with CFRP composites. I am running Static time-history analysis.I use the following properties and section.

Material name: Concrete (Con_ma)
Longitudinal steel rebar: stl_mp
Lateral steel rebar: stl_mp
Section: Reinforced concrete circular section (RCCS).
As built column confinement factor: 1.067
CFRP strengthens column: FRP jacket thickness 0.222mm, FRP elastic modulus (266 GPa) and jacket stain (0.0163), the confinement factor: comes our 1.8803 for CFRP composites.

Element class:inelastic displacement-based frame element (infrmDB), section fibers-200.

I was wondering that, if the confinement factor of as built column (1.067), and the confinement factor of CFRP strengthen column (1.8803. SO, I increased the confinement of the columns, so displacement should be different, but why the analysis results are same, the stiffness and displacement both are same for as built and CFRP strengthened column.
If anybody, could please help me to understand the topic.
Thanks

[huffte]

Hi anantparghi. The first thing which comes to mind is to examine the results and try to determine the weak link. For example, if the weak links are beams, the retrofitting the columns may have little effect on the response. If the original columns never reach inelastic behavior during the analysis, then retrofitting them would produce very little beneficial effect. Can you tell how far into the inelastic range the original columns are loaded during the static time history analysis? Perhaps by examining hysteretic curves for the columns?

Best of luck anantparghi.

[anantparghi]

Hi there,
I am running static time history analysis of reinforced concrete single column as built columns and CFRP strengthen columns.

As built column experimental results shows that the strength of columns is degraded after 3% drift, whereas for as built column numerical results shows that there is no degradation on strength, and it is becoming uniform after 4% drift. In addition, numerical results shows more load carrying capacity of as built columns compared to experimental results for as built column. As I understand, the experimental and numerical results of as built column should be more or less same. Anybody, could please help.
Thanks
Anant

[huffte]

I would say as a first try at finding the difference, make certain that material properties in your numerical model match those of the experiment. Use actual yield stress of reinforcing bars, for example, not the minimum specified. The same for the concrete - did you have cylinder breaks for the concrete used in the test or are you using the specified minimum.

If all material properties are verified to be identical between the two, then make certain that the boundary conditions between them are identical as well.

Best of luck anantparghi.