Column Moment Ratio For Creep - RAPT Help 1

[arik79]

Hi,

Can anyone please guide me for appropriate moment ratios for creep in columns? This factor affects the buckling load calculation in columns using RAPT. I wish to understand how RAPT interprets the factor. i.e How RAPT uses it in its calculations. I understand creep in columns leads to more lateral deformations, and in a fudge sort of way, a lesser buckling load.

Any assistance is appreciated.

 

[rapt]

You could ask RAPT support!

 

[r13]

Based on my limit knowledge, creep is a time dependent phenomenon in concrete structure, that having substantial sustained dead load; the results are elastic shortening and material relaxation at the time of interest, and buckling is usually not a concern. However, I need to refresh my understanding on how it has something to do with moment/flexural though.

Yes, ask RAPT (not rapt

 

[Structimes]

I would also like to understand how the moment ratio for creep value should be determined for column designs in rapt. I have seen examples using 0.1.

 

[Trenno]

Correct me if I'm wrong but isn't simply the beta factor from AS3600 CL.10 = Dead Load / (Dead Load + Live Load). Typically ranging from 0.6-0.8. Residential buildings usually have a higher ratio compared to more live load intense buildings like offices/retail.

Better yet, play around with different values from 0.1 to 1.0 and see the sensitivity for yourself!

 

[rapt]

When a software company has a perfectly good and helpful support service, why do people ask questions like this on a site where most of the people responding have never used the software?

And secondly, why would designers who are supposed to be sensible logical thinkers simply put in meaningless numbers just because they like the result.

I am really starting to worry about the direction of the engineering profession!

As Trenno said, it is the betad factor in AS3600 slenderness calculations. Other codes have similar factors under other names.

 

[Structimes]

Thank you for your help