Topic: Smeared reinf. in circular cross section

Dear Mr/Ms.

I have a circular cross section defined in the plane x-y, with a single circular hoop.
To assign the smeared reinforcement:
1.-For the reinforcement ratio should I use r=(2 x bar area)/(External diameter x spacing between hoops). Or instead of the External diameter (D) should I use 0.8D as per ACI?
2.-the unit vector to define this transverse reinforcement should be x 1 y 1 z 0?

Thank you very much for the help,

VVR

Re: Smeared reinf. in circular cross section

Dear VVR, it is not clear from your question if you have already looked into ATENA Troubeshooting, 2.2.6 How do I calculate the reinforcement ratio when defining smeared reinforcement?

If you seek advice with your particular modelling, please send us some sketches illustrating the geometry and loading + explain the analysis targets (see also Troubleshooting, 2.1.1). Above all, it is not clear if you are modelling just a 2-d cross section or preparing a 3D model or use some other approach?
If you model the section in 1D, I think it makes more sense to represent the hoop as a 1-D bar, as replacing it with 2-3 smeared reinforcement layers would probably mean more work.

Regards.

Re: Smeared reinf. in circular cross section

Dear Sir,

Yes I have already look at the troubleshooting 2.2.6. But from this I would have to say that it is not clear the part where we assign the unit vector in the direction of the reinforcement.

For my particular case:
It is a 3D model.
The cross section is in the x-y plane.
The height of the column is in the z-direction.

From your answer, what I understood is that I should use reinforcement ratio as r=(2 x bar area)/(External diameter x spacing between hoops). Using the entire diameter of the column , and not the 0.8D that ACI specifies. Also, that I should notuse the volumetric ratio, but the definition given by Troubeshooting, 2.2.6.

Thank you very much,

VVR

Re: Smeared reinf. in circular cross section

Dear VVR,
1. as already mentioned, I think in this case the easiest way is to represent each hoop with a discrete bar.

2. If you wish to approximate it using smeared reinforcement, you need to represent it with 2-3 layers of smeared reinforcement, each with a different direction in the X-Y plane - corresponding to some part of the hoop. Of course, the sum of these 2-3 reinforcement ratios should give the volumetric ratio.

3. Your formula with external diameter approximates both the column cross section and the hoop shape as squares. Then, it gives the same ratio for both X and Y directions.

Regards.

Re: Smeared reinf. in circular cross section

Dear Mr.

I have a few queries:

1.-In Material Input Data/1D reinforcement/ Element Geometry; where could I found more information about:
The quadratic element check box
The Default application check box

2.-For the Problem Data/Solution Parameters/Solver. In the ATENA GID User Manual, it is referred that it should be used the ICCG or DCG methods when we have a large 3D problem. So “large” means in terms of finite elements, and if so, how many elements would it be “large”.

3.- When I create the mesh of my model, it creates triangular elements that are defined in a material 0 (not associated with any created material). This gives me an error when I tried to run it.
I try by deleting these elements, and I got another error in the program: “(Thread 1) CCFEModelExc: Invalid group_id(s) 231 331 801 901 specified in Source line:251, file: ..\..\Sources\CCFEModel\check(CCFEModel).cpp, last modified at: Thu Nov 19 15:59:00 2015”.
I am using ATENA Studio 32bit Version 5.6.0

Thank you very much for the help,

VVR

Re: Smeared reinf. in circular cross section

Dear vvr,
ad 1.: if you have specific interest in using quadratic elements for reinforcement, please explain?

The option to activate a reinforcement element in a later Interval is of use when modelling a construction process sequence.

Ad 2.: We currently recommend to use the PARDISO solver unless there is any specific reason to choose another one.

Ad 3.: Please see ATENA Troubleshooting, 4.2.5 GiD claims: You don't have assigned Material 0 at Element xxxx For first number of unassigned element see *.dat file.

If you have further problems/questions, you can follow Troubleshooting, 2.1.1 to send us your model etc.

Regards.

Re: Smeared reinf. in circular cross section

Dear Mr.

For the concrete model Cementitious 2 combined with smeared reinforcement: Does it account for the increase in strain and stress that the smeared reinforcement provides to the concrete?
If it does, where could I see the formulation of this?
I have reviewed Athena Theory, and for what I understood it only considers the effects of confinement in the cementitious 3 model.

Thank you in advanced,

VVR

Re: Smeared reinf. in circular cross section

Dear vvr,
confinement is considered by all materials of the NLCem2 family (and also SBETA), please see ATENA Troubleshooting, 2.2.7 How to include confinement in the analysis? for basic information and ATENA Theory, 2.2.4 Plasticity Model for Concrete Crushing for details (especially Fig. 2-22 Plastic predictor-corrector algorithm.).
The NLCem3 material model has some further improvements, which can make a difference in some specific situations (please explain why you suspect you need that?).

Regards.

Re: Smeared reinf. in circular cross section

Dear Dpryl,
Regarding my last question, would you recommend any reference in order to understand better the beta parameter.

Another question that I have is regarding the material CC3DNonLinCementitious2. When the program does the iterations to find the plastic multiplier increment, the parameter c that depends on the equivalent plastic strain, Is it calculated with the equivalent plastic strain from the last converge step (n), or it changes with the plastic multiplier increment at each iteration (equivalent plastic strain from the last converge step (n) plus plastic multiplier increment times mij? (Algorithm 1 equations 2.59 -2.70, ATENA Theory).

What would you recommend in order to avoid the error message: “CCMaterialExtendedAExc:CC5ParamYieldF::project_stress_on_f-division by zero Source line 147, file: …\..\Sources\CCMaterial\CCElastisotropic\CCGENPLASTICHV\CC5ParamYieldF.cpp, last modified at Thu Nov 19 15:59:55 2015 while computing request 1 for element id:3367, group id:435, name:” I am comparing the behavior from a test and the model, and the model doesn't go as far into the drift ratios as the ones obtained in the experiment, due to this error.

Thank you in advance for all your help,

Kind regards,

VVR

Re: Smeared reinf. in circular cross section

Dear VVR,
1. I guess you have already read ATENA Troubleshooting, 2.2.7.1 The influence of the volume change during crushing (Beta) and ATENA Theory, 2.4 Drucker-Prager Plasticity Model?

2. I am not sure which variable or formula you denote as "c" (there is no such symbol in the referred equations)?

3. I assume you have already checked the most common problem sources following Troubleshooting, 2.4.6 Floating point problems - Division by zero, Loss of >7 digits on the matrix diagonal, CCFEModelExc: CCPardiso solver error: zero pivot,  Warning: Sign of diagonal changed when reducing equation, Floating point exception: Multiple floating points traps, Zero or negative jacobian,  InvertA: zero determinant, CCMaterials Extended AExc: CC5ParamYield F: project_stress_on_f_division by zero, and similar?

Please also see Troubleshooting, 2.4.2 I get the message "The execution is killed due to violation of stop iteration criteria", what does it mean? and 2.1.19 Problems reaching convergence and understanding ATENA convergence parameters.

If you still have problems, you can follow Troubleshooting, 2.1.1 to send us your model etc.

Regards.