Creep coefficient over time 1

[dccd]

I came across 2 creep coefficient diagram. First one is from Eurocode, second one is from elsewhere. I think the second one make sense, As the time progress, the creep coefficient shall increase, hence, the effetive modulus of concrete shall decrese. Can someone explain it ? I am confused.

 

[Settingsun]

I think your top left diagram is showing the effect of age at loading the concrete. Creep is less if the load is applied to old concrete, but the reduction to zero at 100 days is overly optimistic.

 

[dccd]

Which is correct ? First or second ? In the first one, the creep coefficient decrease with time, the second one increase with time.....If the coefficient decrease with time, effective modulus will be increasing with time, it seems doesnt make sense

 

[Settingsun]

Creep always increases with time. The diagram showing it reducing is because it is showing final creep of concrete that is more mature when loaded. If you load concrete one day after pouring it, the creep after a year will be massive. If you load ten year old concrete, the creep after one year will be much less.

 

[Settingsun]

I see now, it's a nomogram. The creep doesn't go down to zero.

 

[Settingsun]

Your second graph is the ageing coefficient used in the age-adjusted effective modulus method. Neither of the graphs you posted is actually creep vs time. Creep vs time looks like this:

 

[dccd]

Do you mean the first graph ( from EUrocode) present the creep of concrete that is loaded at different age (creep of concrete will be less when the concrete is older, concrete loaded after sometime ) ? While the second graph showed that the creep of concrete over time (concrete loaded at t =0 ) ?? Am I right ?

Thus, (in second graph, as the time progress, creep will be higher? ) (In first graph, for older concrete, the creep will less noticeable than fresh concrete ? )

 

[Settingsun]

Do you mean the first graph ( from EUrocode) present the creep of concrete that is loaded at different age (creep of concrete will be less when the concrete is older, concrete loaded after sometime ) ?

That's correct for the final value of the creep, but you have to follow the five steps to use the eurocode nomogram. You can't just read directly from the graph on the left. Creep vs time looks like my Figure 2.2.


The second graph (from Bazant) is the ageing coefficient, not the creep coefficient. They're different things but the shape is similar to creep vs time. I think you should ignore the Bazant graph for the moment as it's a more advanced topic in creep. It's used to modify your equation 6.8 to improve accuracy of creep calculations:

Eurocode equation B.7 is what you are looking for.

 

[dik]

What is equation B.7? Can someone post it? Thanks...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

Eurocode:

Australia:

 

[dik]

Thanks steveh... a new little SMath program...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

For the first both for any comments (I'm not quite sure of what I'm doing). I don't know what alpha1 and alpha2 are for. When the bugz are out, I'll post the SMath program.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Manitou90]

Alpha1 and Alpha2 are use to calculated the nominal creep. They are used in Eq. B.3a and B.3b.

Edit: Obviously only used in B.3b, but in that set of equations

 

[dik]

thanks Manitou... will update

Updated... can anyone provide information about what the numbers mean? I well aware of the hazards of using numbers you don't understand. I'm faintly curious about creep and I was happy to see some quantitative formulae. I've arbitrarily modified the units to 'work' and SMath treats percents as a decimal number, and shouldn't need to divide it by 100.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Correction... forgot to change the alphaprimed2

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

Dik, I only posted the creep development over time rather than the actual creep coefficient. If you're going to this much trouble, you might as well calculate the whole show. See attachment.

EDIT: Link didn't work - see a couple of posts further down.

 

[dik]

steveh: can you re-post the link; I cannot get it to download.

Thanks... there wasn't much trouble...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

Let's try this link. I'm assuming spaces or ampersand in the filename were the problem with the last upload.

https://files.engineering.com/getfi...7-afb7-a355a43e0000&file=AS3600_EC2_creep.pdf

 

[dik]

Thanks, got it... not to read and maybe try to understand... again, thanks. I'll post the final SMath when it's completed and checked. The reason I wrote it is that I like 'funny' formulae and I find SMath great for them.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Is there information about the values in the below formula, in particular epsiloncc and sigma0? Is there also an article that expains the methodology? I've nearly completed the formulae (as a challenge to myself) and I don't have a feeling or understanding of what I'm calculating.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik