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RC coulmn design-limit of slenderness and effective creep coefficient

11 REPLIES 11
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Message 1 of 12
AIIAK
602 Views, 11 Replies

RC coulmn design-limit of slenderness and effective creep coefficient

Hey

 

I´m working on the design of RC columns. I have noticed that the limit of slenderness which Robot calculate is different than the one I calculate accourding to (5.13N) EN 1992-1-1:2004 AC:2008. Anybody can tell me how Robot calculate this value when EN 1992-1-1:2004 AC:2008 is used?

 

Also, how does Robot calculate the effective creep coefficient φef  ? It seems that φ(∞,t0) is just used instead.  φef  should be calculated accouring to (5.19) EN 1992-1-1:2004 AC:2008. 

Thanks in advance

Ali Ihsan

11 REPLIES 11
Message 2 of 12
Rafal.Gaweda
in reply to: AIIAK

(5.13N)

 

Robot uses the same formula.

If you think that something is wrong please send us example model.

 

 

 how does Robot calculate the effective creep coefficient φef  ? It seems that φ(∞,t0) is just used instead.  φef  should be calculated accouring to (5.19) EN 1992-1-1:2004 AC:2008. 

 

If you import manual combinations to RC module φ(∞,t0) is used

If you import simple cases to RC module Robot generates ULS and related SLS QPR combinations and φ according to formula 5.19  is calculated

 



Rafal Gaweda
Message 3 of 12
AIIAK
in reply to: Rafal.Gaweda

Hey Rafal

 

Thanks for your reply. The model Im working on is very big, so I have made a model for the column only using the same forces, so I get the same problems.

 

Concidering the limit of slenderness, I don´t quite get the same result as Robot do.

 

Considering the creep coefficient, I do import manual combinations to RC module. Is there a way to work around this? The model I do work on contain hundreds of load combinations.

 

Best Regrads

Ali

Message 4 of 12
Rafal.Gaweda
in reply to: Rafal.Gaweda


(5.13N)

 

Robot uses the same formula.

If you think that something is wrong please send us example model.

 

 

Are you refering to value 24.13 from pdf or 45.77 from rtd file?

If the value 24.13 is wrong we need the file with these results \ column.



Rafal Gaweda
Message 5 of 12
AIIAK
in reply to: Rafal.Gaweda

I´m Actullay refering to value 45.77 in the rtd file.

Message 6 of 12
Rafal.Gaweda
in reply to: AIIAK

Our calculations:

Formula (5.13N):
Lambda_lim = 20*A*B*C/sqrt(n) = 45.76

Variable:
A= 0.625
B= 1.304
C=2.376
N= 0.716

Input data
Phi =3.0
As = 0.02413 [m2]
omega 0.3497
Mtop = 1678[kN]
Mbot = -1134[kN]
Rm = -0.6758



Rafal Gaweda
Message 7 of 12
AIIAK
in reply to: Rafal.Gaweda

Hey Rafal

 

Thanks for your response. In this case the value given by ROBOT checks out but when I look into other cases the value I get from ROBOT is different from the one I get from my manual calculations.

 

Perhaps I misunderstood something. How are M01 and M02 defined in ROBOT? Is M01 always the moment at the bottom and M02 is on the TOP? Does the calculations change if │M02│≥│M01│?

 

I have attached the ROBOT model for some other columns than the one we already have considered. I couldn´t upload the model I work on as it is to large. But the columns in the attached model shows the same result considering lambda_limit.

 

Best Regards

Ali Ihsan

Message 8 of 12
Rafal.Gaweda
in reply to: AIIAK

mtop.jpg



Rafal Gaweda
Message 9 of 12
AIIAK
in reply to: Rafal.Gaweda

Hey Rafal

 

Thanks for the clearfication. Problem is that I still get different values. I have observed that the values of the lambda-limit changes between the simplified second order analysis method based on nominal stiffness and nominal curvature? I think that shouldn´t happen.

 

You can observe that when you look at the attached model. You can change between the two methods and you will notice a different for column 2-4. Column 1 shows the same value for both method which get me even more confused.

 

 

Message 10 of 12
Rafal.Gaweda
in reply to: AIIAK

Message 11 of 12
AIIAK
in reply to: Rafal.Gaweda

Hey

 

I don´t think that doesn´t have anything to do with this issue. Even If I use Method of calculationg biaxially bent rectangular columns "Based on stress distribution". One of the simplified second order analysis methods will always be switch on.

 

Please see the attachment.

Message 12 of 12
Rafal.Gaweda
in reply to: AIIAK


 

You can observe that when you look at the attached model. You can change between the two methods and you will notice a different for column 2-4. Column 1 shows the same value for both method which get me even more confused.

 

 Got it.

You are right. The value should be the same. 

Need to be corrected.



Rafal Gaweda

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