1 (edited by hamedsn 2019-03-17 06:26:22)

Topic: Mass concrete hydration

Dear Sir/ Madam,

I hope this message finds you well.

Is it possible to input temperatures below zero and/or cryogenic conditions in the transport analysis?

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
you can prescribe temperatures below 0 in Transport, no problem with that.

However, if you are interested in the influence of frost on hydration heat development, as far as I know, the properties generated by ConMix do NOT specifically consider that. You would most likely need to adjust the properties manually. Even the heat corresponding to the phase change has to be taken into account by adjusting the Capacity function.

Similarly, when you later import the Transport results into your Static or Creep model, you have to define the corresponding functions for the material model with teperature-dependent properties (prototype NLCem2UserWithTempDepProps) by yourself.

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Many thanks for the reply and constructive comments. I want to consider hydration heat and moisture in a gallery of a mass concrete structure,i.e.,  a RC dam.

Based on the documentation I have to use the CERHYD model. I have gone through the documentation but I just can't understand how the model works:

1- What are the differences between the types of definition "file", "user" and "none"? which one do you recommend?
2- I would be really grateful if you could introduce me some references to give me an insight regarding the parameters used in the CERHYD model. The theory of the model based on the theory manual without an example is a bit difficult to understand.

3- How does the "ConMix" model is linked to the model generated in the GID? should the "ConMix" program be put in the same folder as the GID file? Is there a separate file generated?

I'm using ATENA version 5.1.3f. Many thanks for all your support.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
if you plan to use the CCTransport material model with CerHyd and ConMix, you have to upgrade to the current ATENA version, 5.6.1h. Although the CCTransport material had already been available in ATENA 5.1, its advanced options (like all CerHyd ones) were not fully implemented yet.

ConMix is include in the current ATENA installation and starts from the CCTransport material dialog when you choose "File".

Once you install the current version, I suggest to look at the hydration example model (ATENA Science Example Manual, 3.2 Heat and Moisture Transport Analysis incl. Hydration - both the document and the referred example model are included in ATENA installation).

If your expired ATENA maintenance does not allow you to use the current version, please contact us for a renewal offer.

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Many thanks for the reply.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Dr. Pryl,

I hope this message finds you well. I want to apply monthly time-dependent temperature variations to a part of an arch dam in the transport model.

1- From what I could understand from the GID manual, the only way to define temperature-time curve is through using the “Moisture temperature boundary for surface” condition or is there another way too?

2- If the “Moisture temperature boundary for surface” is used, ambient temperature function can be defined from “function from material”. It’s been specified in this dialog that” this material is only for writing user function to the input file, do not assign it to the model”. This being the case, how can I assign the material to different parts of the dam?

Moreover, in the static model and the “Reinforced Concrete” material dialog, why there are 6 smeared reinforcements?, what do they denote?

Many thanks for all your support.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
ad 1.: Yes, if you know the temperature of the surrounding air, the Moisture Temperature condition is the one to use. Note you can disable the Humidity DoF in Interval Data if you are only interested in Thermal analysis.

In case of Fire loading, it is usually better to use the Fire condition (essentially the same as the above, but with predefined ETK and other fire temperature history curves).

In case you know the surface temperature, you can use the condition Temperature for surface.

Ad 2.: The text is to explain that this special "material" can only be used to define functions (to be used in other materials or conditions), not to be assigned to some Volumes. If you can suggest some better wording (to let more users understand correctly after reading it), please let us know.

Ad Smeared reinforcement: please see ATENA Troubleshooting, 2.2.6 How do I calculate the reinforcement ratio when defining smeared reinforcement? for basic information about representing some bars as smeared reinforcement.

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Many thanks for your prompt answer and the constructive comments. I simply want to define a curve showing temperature variations as a function of time and apply it to a surface, i.e.:

Time (days)       Temperatures (degrees centigrade)
30                      0
60                     -1
90                    4.2
120                   11.7
150                    17
180                  22.4
210                  26.2
240                  26.9
270                  24.2
300                  17.7
330                  10.8
360                    4.7

how can I define this curve in ATENA-GID interface?
Is it possible to use the fire boundary element condition to define the curve by manually adjusting the values, or is there a better way?

Moreover, I guess I have to use smaller load steps or use finer meshes in the model to capture below zero temperatures, am I right?

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
1. the temperatures are measured (or calculated? or given from a code?) of the concrete (at its surface), or the air near the concrete surface (or in some distance)?

2. I understand you are only interested in the long-term average temperatures (year cycle), i.e., not interested in day cycles or any gradient changes?

3. The Fire and Moisture Temperature boundary conditions are internally identical, they only differ in the predefined curves.

4. If you are interested in long-term quasi-static temperature fields, where no steep nor quickly changing gradients are expected/important, I guess the mesh can be like for your Static or Creep model, or possibly even coarser.

5. Regarding the step length, I would start with something like 1 step per day and see.

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Sorry for my late reply.

1. Temperatures mentioned in the previous post are average monthly temperatures of the air obtained from meteorology measurements and l’ve ASSUMED them to be air temperatures near the concrete surface.

I would be really grateful if you could explain about the different cases that you’ve mentioned in the previous post and the possible reliance of the obtained results on the respective case considered.

2. I want to investigate several cases including (a) long-term temperatures (year cycles) and (b) day cycles where there are usually gradient changes, for example between -10 and 10 degrees centigrade.

3. I’ve manually edited the fire and boundary conditions to define the time-temperature curve. I do not know any other way.

Many thanks for all your support.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
ad 1.: then, the Condition "Moisture Temperature Boundary for Surface" is clearly the first choice.

Ad 2.: OK.

Ad 3.: In the Moisture Temperature condition, you can activate AmbiTemper FUNCTION and define the corresponding function(s) in Data - Materials - Functions.

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Many thanks for your email.

The problem is that I don’t know how the “functions” work.

If the moisture temperature condition is activated, the default value for the ambient temperature is equal to 20 degrees centigrade and it is reasonable to consider temperature variations as coefficients multiplied to the ambient temperature to be used as Y values along with X values (which should be time values in seconds) in a tabular form and there is no need to use the X and Y multipliers in the “functions” dialog box.

For example if I want to define that after an hour the temperature rises to 25 degrees centigrade should I define it as follows?:

X (s)                   Y (temp)
0                           1
3600                    1.25

X multiplier =1
Y multiplier=1?

I feel that I’m missing something here. I really appreciate all the guidance you provide.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
I guess you have already found out how to use the functions? Unlike most Conditions in ATENA, the Fire and Moisture-Temperature ones are total (i.e., not incremental). Therefore, absolute temperatures of the heat source/air (and not increments/differences) are to be defined there.

If the Moisture-Temperature conditions does not allow a function for the ambient temperature history, I agree the best way is to use the Fire condition. There, you define the min. and max. temperature, and a time history function (where 0 on the vertical axis corresponds to the min. temperature and 1 to the max.).

Best regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Unfortunately, I haven’t been able to figure out how the functions work. I’m familiar with the total condition. I’ve used it before in the “fire boundary for surface” condition.

I just don’t know how the values in the functions dialog box work. If I want to apply “moisture temperature condition to a surface with an initial ambient temperature of 20 which rises to for example 30 degrees in two hours what the values should be in the functions dialog box (the initial temperature of concrete is also 20 degrees centigrade)? Should they be as follows?:

X (time, unit seconds)                    Y (temperature, unit degrees centigrade)
0                                                      20
7200s                                               30
Multiplier X=1
Multiplier Y=1

OR

X (time, unit seconds)                     Y (temperature, unit degrees centigrade)
0                                                      1 (20 divided by the initial ambient temperature)
7200s                                              1.5 (30 dived by the initial ambient temperature)
Multiplier X=1
Multiplier Y=1

When I define any of these, I get the error” underflow or overflow arithmetic operation” in the very first step of the analysis.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
1. please keep in mind the Initial Temperature is defined in the Material dialog at the corresponding tab.

2. If you are only interested in temperature but not moisture, disable the unneeded degree of freedom in Interval Data.

3. I think the following should be equivalent, but I am going to check with our colleague responsible for the ATENA-GiD scripts:

A. Ambient temperature 1, function 0;20 7200;30

B. Ambient temperature 20, function 0;1 7200;1.5

C. Ambient temperature 30, funtion 0;0.66667 7200;1

4. What is your step length, mesh, ... (Troubleshooting, 2.1.1)?

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

1- I define the initial temperature for the concrete itself from the data-material-solid concrete-cctransportmatrial-initial temperature tab. For the “moisture temperature boundary for surface” condition the default value for the initial temperature is 20 degrees centigrade and I do not change it; I enable the ambient temperature function and define the function as I’ve mentioned in my previous post by entering the x and y data in a tabular form. I assign the condition to the surface I want but I do not assign the function to the model.

2- I fix the moisture DOF.

3- Thank you very much.

4- The mesh size and the step length vary in my model. But I don’t think the problem is related to the mesh size or the step length. I analyze my model without any problem by defining the curve using the “fire boundary for surface” condition. I just want to learn how the functions work as well.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed,
ad 1.: There is no initial temperature definition in the moisture temperature condition. Do you mean the Ambient Temperature setting?

What do you mean by "I do not assign the function to the model"?

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

1- Yes I mean the ambient temperature setting.

2- I mean the note in the "functions" dialog box which says "this material is only for writing user function to the input file. Please do not assign it to the model".

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed, you can follow Troubleshooting, 2.1.1 to send us your model etc. Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

I sent the model to your email via yahoo.


Best Regards,
Hamed

Re: Mass concrete hydration

Dear Dr. Pryl,

I hope this message finds you well.

Is it possible to use the convection term for "heat convection and radiation" in "moisture temperature boundary for surface"

condition to simulate the convection between concrete-water interface or it can only be used for concrete-air interface?

Many thanks in advance for your reply.


Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed, if you set the parameters accordingly, I guess the condition should give you at least a reasonable approximation. Or are you specifically interested in some effects important for water and negligible for air?

Regards.

Re: Mass concrete hydration

Dear Dr. Pryl,

Many thanks for your reply. I'm only interested in temperature variations in water and air and convection between concrete-air and concrete-water interfaces.

From what I have found in the literature with regard to this is a typical range of 10-30 (watt per square meter per degree Celsius) for concrete-air interface and 200-1000 (watt per square meter per degree Celsius) for concrete-water interface.

I have also emailed my model and have queried about crack spacing in plain mass concrete for which I would be really really grateful if helped me with it. 

Many thanks for all your wonderful support.

Best Regards,
Hamed

Re: Mass concrete hydration

Dear Hamed, please be patient - there are many questions from users with valid maintenance, who of course have priority. Regards.