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## Robot Structural Analysis

Mentor
Posts: 181
Registered: ‎10-08-2011

# Columns Calculation Note

887 Views, 24 Replies
02-10-2012 02:38 PM

Hi all ;

Im on RSA2011 - SP6 and  i'm traying to work with Reinforment Columns module under EC8.

After exporting a column from RSA the remarks ive found are :

1. even if my live loads are defined on categorie "F" wich means a coefficient Psi-2 = 0.6 ; loadind table on the RC module shows 0.30 which not modifiable .... ( is there a way to correct it ? ) -- please See attachement

2.By examining the calculation Note ; i've found these remarks -- please See attachements ::

2.a Problem in calculation final excentricity

2.b Very big Moment magnificient coeffient

2.c the effective creep is greater the conventional one wich i think not correct.

2.d How does RSA determine the coefficient Js ? it is done after obtaining the reinforcement ?

Ive done calculation of this columns in comparaison on a excel sheet , an i obtained more reasonable values ie : Magnificient coeff = 2.834 ; effective creap = 0.226 ; [can send snap shot inf required].

I need to be figure out these pb -- have several columns to calculate

Thank you for help

Product Support
Posts: 4,044
Registered: ‎12-17-2010

# Re: Columns Calculation Note

02-13-2012 05:56 AM in reply to: faisal.aaouatif

Could you attach the rtd file with the column you attached the results for please?

Artur Kosakowski
Mentor
Posts: 181
Registered: ‎10-08-2011

# Re: Columns Calculation Note

02-14-2012 04:15 AM in reply to: Artur.Kosakowski

Good Morning/Evening Artur ;

The Rtd file Is sent by using a FTP site (Big model even after compressing ) given to me by private mail.

the calculation was done for the column 89 (Ground Floor).

when exporting from the model , at the column RC module the height of this column is equal to 5.7041m (even if the difference between upper level and bearing point is equal to 5.335 ? i dont know why , so i change it to 5.335m and the width of the beam to 0.70m

the coefficient of buckling i the direction y is equel to 4.424

the buckling analysis in the direction z is not important... at this stage.

So here is the summary of what i asked for and other points:

1.Coeff Phi2 change after export to Rc Column module ( See table of loads)  [Priority 3]

2.is there a way to design the column exported with a steel resistance , the same as defined in job preference of the model [ in the model = 420MPa but in the RC Column design = B450C....]? )  [Priority 2]

3.How can we take seismic dispositions into consideration ( can't see any button for that ?) [Priority 2]

Other points .... :

4. Total excentricity : i think , its a final result , computed from final magnified moment and axial load.

5.the critical effort of buckling (243.99t) is lower than  dimensionning one (362.28t) -- > i think that this should mentionned as a clear warning before continuig the analysis [Magnificient moment method has no meaning if there is such problem of stability ...] [Priority 1]

6.How RSA compute the effective coefficient of creep ( is it a average/min/max value of all combinations , the value for the unforable combination ) -- This coeff has a serious effect on other coeff. [Priority 1]

7.in the formula computing the rigdity ( EJ )shown at the calculation note ; it seems that the module Ecd is not divided by (1+coeff effective creep). - Is RSA consider that the column isolated even if its a part of hyperstatic structure ? (Reminder : See Eurocode2 - Art5.8.7.2.(4)) [Priority 1]

8.Is RSA computing the reinforcement by adopting the maximum moment at the column or by using an equivalent moment (0.60M1+0.40M2 as indicated on EC2-5.8.7.3 ? [Priority 1]

sorry for being too long

Product Support
Posts: 4,044
Registered: ‎12-17-2010

# Re: Columns Calculation Note

02-15-2012 01:00 AM in reply to: faisal.aaouatif

the calculation was done for the column 89 (Ground Floor).

when exporting from the model , at the column RC module the height of this column is equal to 5.7041m (even if the difference between upper level and bearing point is equal to 5.335 ? i dont know why , so i change it to 5.335m and the width of the beam to 0.70m

5.335 (node to node; top node in the middle of the column height) + 0.5*0.7383 (height of the beam 1174) = 5.7041 (see the attached picture)

the coefficient of buckling i the direction y is equel to 4.424

Do you mean 4 times the column height  (ky = 4.424) or just 4.424 m (Ly = 4.424 and ky =1)?

Artur Kosakowski
Mentor
Posts: 181
Registered: ‎10-08-2011

# Re: Columns Calculation Note

02-15-2012 03:17 AM in reply to: faisal.aaouatif

Hi Artur;

i meant ky=4.424

Thanks

Product Support
Posts: 4,044
Registered: ‎12-17-2010

# Re: Columns Calculation Note

02-15-2012 03:38 AM in reply to: faisal.aaouatif

so i change it to 5.335m and the width of the beam to 0.70m

the coefficient of buckling i the direction y is equel to 4.424

the buckling analysis in the direction z is not important... at this stage.

1.Coeff Phi2 change after export to Rc Column module ( See table of loads)  [Priority 3]

As you defined combinations in the model I assume you wanted to use them for the design as well so you can import them instead of simple load cases. This is what I’m going to do for checking next points.

2.is there a way to design the column exported with a steel resistance , the same as defined in job preference of the model [ in the model = 420MPa but in the RC Column design = B450C....]? )  [Priority 2]

Yes, you need to edit the reinforcement bar database and add bars with such steel grade.

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Provided-Real-Reinforcement-Bar-Diameter-Lis...

Artur Kosakowski
Product Support
Posts: 4,044
Registered: ‎12-17-2010

# Re: Columns Calculation Note

02-15-2012 03:54 AM in reply to: faisal.aaouatif

3.How can we take seismic dispositions into consideration ( can't see any button for that ?) [Priority 2]

This functionality has been introduced in Robot 2012.

Artur Kosakowski
Product Support
Posts: 4,044
Registered: ‎12-17-2010

# Re: Columns Calculation Note

02-15-2012 06:32 AM in reply to: faisal.aaouatif

4. Total excentricity : i think , its a final result , computed from final magnified moment and axial load.

Correct.

5.the critical effort of buckling (243.99t) is lower than  dimensionning one (362.28t) -- > i think that this should mentionned as a clear warning before continuig the analysis [Magnificient moment method has no meaning if there is such problem of stability ...] [Priority 1]

This is not separately stated however in such case you should have both calculation error and information in the calculation note that the capacity of the column is too low. This request has been added to the wish list.

6.How RSA compute the effective coefficient of creep ( is it a average/min/max value of all combinations , the value for the unforable combination ) -- This coeff has a serious effect on other coeff. [Priority 1]

Calculated for each of the combination separately.

Artur Kosakowski
Product Support
Posts: 4,044
Registered: ‎12-17-2010

# Re: Columns Calculation Note

02-15-2012 07:08 AM in reply to: faisal.aaouatif

7.in the formula computing the rigdity ( EJ )shown at the calculation note ; it seems that the module Ecd is not divided by (1+coeff effective creep). - Is RSA consider that the column isolated even if its a part of hyperstatic structure ? (Reminder : See Eurocode2 - Art5.8.7.2.(4)) [Priority 1]

Correct. The request for implementation of Art5.8.7.2.(4)) is added to the wish list.

8.Is RSA computing the reinforcement by adopting the maximum moment at the column or by using an equivalent moment (0.60M1+0.40M2 as indicated on EC2-5.8.7.3 ? [Priority 1]

The check is done in 3 locations: top and bottom for the values of bending moments from these locations and in the middle according to the above formula or real value of bending from the model if larger.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

Artur Kosakowski
Mentor
Posts: 181
Registered: ‎10-08-2011

# Re: Columns Calculation Note

02-23-2012 01:14 AM in reply to: Artur.Kosakowski

Good Morning Artur ;

having a problem to set the steel grade discussed above. see attachement

Another issue

when exporting a column RSA does not give me the hand to use my own combination , this why i'm using simple cases? How can i use mines ?

thanks