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Concerning the Design Calculations that you sent me,

Question:

Hello Nivedita,
Thank you once again for the Timely reply of the Querries.
Concerning the Design Calculations that you sent me,
How do you Compute the Values of y, z, Ixx and Iyy as parameters to use in Checking the Stress Limitations?
What Formulars do you use both for Cracked Section and UnCracked Sections?
Kindly Illustrate with Sketches of what the parameters Mean and their Formulae to Clarify as we follow them.

FOR COLUMNS, SEE IMAGE BELOW.


FOR R.C BEAMS, SEE IMAGE BELOW.
Thank You very Much for your Reply.

Answer:

Dear Sir,

Thank you for sending verification request, we shall get back to you on the same from this ticket.


Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Dear Sir,

1. How do you Compute the Values of y, z, Ixx and Iyy as parameters to use in Checking the Stress Limitations?
the values y, z, Ixx and Iyy are from section properties. We can see these values in section property definition > show stiffness properties as shown in the image below. There are two methods to calculate these values, Analytical (based on conventional formulae and FEM based on dividing the section into finite meshed elements for calculations). By default analytical formulae are used for calculation the section property values.
For rectangular section, the NA depth in both directions has come out to be same as center of the section (equal reinforcement in both directions).
The moment of inertia, Iyy & Izz include the area of steel.

2. What Formulars do you use both for Cracked Section and UnCracked Sections?
Depending on the code selected for design purpose, the cracked section Icr is calculated. 
Based on iterations, the NA axis depth, z is calculated. Then Iyy is based on modified NA.


 

Hope this helps. May you have any further query, please feel free to write back to us.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Hello Nivedita,
Thank you very much for the reply.
My humble request is, kindly help me send me the reference (may be a text book or a paper) where where you got the Forrmulae so that I can further refer to it.
Also another question is; Is the formular for calculating the Icr the same for both cracked and uncracked section the same or different.
I use Eurocodes for design.
Thank you very much Madam.
I really appreciate your timely reply.


Hello Nivedita,
I still can not get the Values of Z and Iyy for Uncracked sections and I can not also get Z and Icr for Cracked Sections when i use the Formulae you sent to me While Using exactly the Same Parametere used by the Software. This demonstrates that i am totally Confused.
Kindly advise me with the exact Formulae, the software Uses so that when i am using Hand (Manual) Calculations, I get the same Values as the Software. Irrespective of the Code Used, Kindly Help me with the Formulae for purposes of Manual Calculations.
Thank you Very Much.


Dear Sir,

Usually we require your manual calculations to compare with software calculations. If you could send us the method used by you to manually calculate the cracked and uncracked section properties, we can provide you prompt solution.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Hello Madam,
The it is Like this, Get any beam designed by nGen, Get the same parameters used by the software and plug them in the Formulae you sent me both for Cracked and Uncracked sections, the values obtained by the formulae are different from the ones the software gives in the output,
Kindly clarify on this.
Thank you once again for your committed replies.


Dear Sir,

Kindly share with us these calculations that you have performed to provide you prompt solution.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Good day Nivedita,
i have attached the Manual calculations, specifically for the Cracked section, Output for beam design (Check on page 10 for Values of Z and Icr.) and also the Formulae used in the Manual Calculations.
Kindly crosscheck and advise.
Thank you very much.



Dear Sir,

Thank you for sending the calculations. The upper y and z value is centroid of uncracked section. The lower z values are the depths of NA and part that considers compression. 

Moment of inertia for cracked section is calculated to consider cracked equivalent section. It means that consider the rebar and only compressive region of concrete.



Hope this helps. May you have any further query, please feel free to write back to us.

Regards,
Nivedita
Technical Manager

Click here to give FEEDBACK

MIDAS Software: en.midasuser.com

Hello Nivedita,
Thank you for the reply.
However I am failing to understand it.
May you kindly elaborate with a manual calculation using the data that I used to see how you arrive at the same values as the software?
You may use your own but same data for both manual and software calculations if you so wish.
This way I will hopefully understand.
Thank you once again.


Hello Nivedita,
Kindly pick up design calculations of a beam from nGen and get the same parameters, plug them in the formulae like I did and they did not match to just show me how manual relate to the software results concerning the Stress limitations in beams.
Just a humble request.
Thank you.


May be just guide me on my manual calculations where I am getting it wrong as compared to the nGen output.
Thank you.


Dear Sir,

Please find attached excel sheet and example files explaining the input values to be taken for the calculation.

Hope this helps, may you have any further query, please feel free to write back to us.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Very well elaborated, Thank you Nivedita and your entire Midas Team.
Kindly add in the spreadsheet, the calculations for the Uncracked Section and Share for Clear understanding also.
Thank you very much.


Dear Sir,

There are slight corrections in the uncracked beam and column moment of inertia. Please find attached the modified excel file.

Thank you.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Thank you very much for the reply.
Don't we usually consider the Cracked section for the Column as well (You have not included it in the spreadsheet).
Also the computations for the Uncracked section of Column vary very much, why this very big difference in computations?

Thank you.


Dear Sir,

The computation of column uncracked varies due to calculations in the software. For column cracked, the same formula for beam cracked will be used.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Hello Nivedita,
The computations for the Uncracked section of Column vary very much, why this very big difference in computations?

Thank you once again.



Dear Sir,

kindly provide an image for the query to provide prompt solution.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Here it is as provided in your spreadsheet that you sent to me.
Thank you.



Dear Sir,

The calculations were sample and considered the reinforcement only in one line for columns at either ends.


However, these are placed in 4 rows. The location of reinforcement in the middles two rows were not considered in the calculation. When we do so, the calculation would be as mentioned in the attached excel sheet.



Thank you.

Regards,

Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Hello Nivedita,
Thank you very much for the correction.
But now, What formulae did you use to compute the values of d and dc for the Uncracked beam section as per the Spreadsheet?
below are the d and dc i am talking about as extracted from the Spreadsheet.
Thank you very much.


Also kindly help me with a sketch that demonstrates all the parameters used for computations in:
[i] UnCracked Section.
[ii] Cracked Section.
Thank you Madam and your Entire Midas team.


Dear Sir,

Apologies, however we can provide information related to software solution.

Thank you.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Absolutely.
And that is what we are discussing about.
How did you get d and dc in the spreadsheet was the question.
Thanx.


Dear Sir,

d is the effective depth of beam and dc is the distance to the NA. The calculation of dc was provided in the excel sheet and to find effective depth for beam, d = total depth - clear cover - stirrup diam - center of two layers of rebar = 400 -40-10-20-6.875 = 323.125 mm






Regards,

Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Hello Nivedita,
Thank you very much for the reply.
My last question with this ticket is: How do you set up the clear distance between the two layers of rebars in nGen?
In your illustration sketches, you got the clear distance between rebars as 13.75mm,
How does nGen find this distance? Or if it is in settings in the program, where do I find this setting?
Thank you very much for your elaborate illustration.



Hello Nivedita,
A kind reminder on this ticket with the question below.


Thank you very much for the reply.
My last question with this ticket is: How do you set up the clear distance between the two layers of rebars in nGen?
In your illustration sketches, you got the clear distance between rebars as 13.75mm (ref. spreadsheet also),
How does nGen find this distance? Or if it is in settings in the program, where do I find this setting?
Thank you very much for your elaborate illustration.


Dear Sir,

It is the effective depth of section with respect to the center of layers of reinforcement. In the formula, the clear distance between two rebars  is 25 mm. And we can control this in the design settings as well as in the define/modify reinforcement option as shown in the images below.




Use a1d1+a2d2/a1+a2 formula to find the center of reinforcement. A sample calculation is shown below
area of 1 rebar = x
there are 5 rebars in 1st layer and 3 rebars in the second layer
center of 1st layer of rebar from the concrete edge = 60 mm
center of 2nd layer of rebar from the concrete edge = 95+10=105 mm

Y = ((5x*60)+(3x*105))/(5x+3x)
   = (300 + 315)/8
   = 76.875 mm

Effective depth, d = 400 - 76.875 = 323.125 mm

Hope this helps.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Thank you very  much for all  the elaborations/illustrations.

Hello Nivedita,
Sorry for re-opening this ticket.
Now for the Column Parameters, how did you get the values i have circled in red as per the same spreadsheet that you sent me?
Just the way you elaborated for the beam section, Kindly do the same illustration for the Column.

Thank you once again.


Dear Sir,

These are general calculations for each part of rebar area. Kindly let us know expected value.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Hello Nivedita,
Just want to know how you Compute dc, d' and d as per the spreadsheet.
Thanx.


Dear Sir,

Thank you for your patience

  • dc is same for both parts of calculation.
  • d' is the effective cover considered till the 2nd layer of rebar. Distance between rebars c/c is calculated by keeping the rebars at equal spacing. Therefore, full depth - both side cover /3 = (500-66-66)/3 = 122.667 mm. Now add this from the edge of the column section to get 66+122.667 = 188.6667 mm.
  • d is the effective depth of the 4 bars considered at 2nd layer. full depth - d' = 500-188.667  = 311.333 mm
For more exact value of Izz, consider the correct number of bars at each layer.
As these are basic calculations, it is recommended that basic analysis and design journals be referred for verification purposes.

Thank you.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Thank you very much Nivedita for the timely reply.
May you Kindly recommend to me some basic analysis and design journals to be be referred to for verification purposes.
Very much appreciated.


Hello Nivedita,
Also what formula did you use to compute the dc for the Column (=0,25m)
Thank you very much once again.


Dear Sir,

It is 500/2 = 250 mm.


Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Thank you very much Nivedita for the timely reply.
I thought that you are supposed to use the formula like for beams (Why not use the formula-Just inquisitive to know).

May you Kindly recommend to me some basic analysis and design journals to be be referred to for verification purposes.
Very much appreciated.
Thank you.


comment has been cloned to a new ticket ##28293834

Dear Sir,

You further queries shall be answered in the ticket #28293834.

Calculations for both are same. The reinforcement arrangement of the column is equally distributed, which is not the case for beams, that is why we can simply divide the section depth by 2.

Regards,
Nivedita
Technical Manager

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MIDAS Software: en.midasuser.com

Thank you very Much Madam.
Creation date: 6/9/2020 1:48 AM (Rohan)      Updated: 6/17/2020 2:46 PM (dklee@midasit.com)
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