Rc Members - Required Reinforcement - Circular columns

[RRufino]

Good morning,

I'm posting this to ask several things related with "RC Design"->"RC Members -> Required Reinforcement".

By default you can have required reinforcement along b and h, this is valid for rectangular/square sections, how can have required reinforcement to circular columns?

When defining R/C member type i've selected nominal curvature to second order analysis...i tried help to get more information but it says page not found...what is happening?

How can i see detailed calculations related to second order analysis...displacements, slenderness and other parameters defined on point 5.8.8 of Eurocode 2 (EN 1992-1-1)?

Thanks in advance.

[Artur.Kosakowski]

By default you can have required reinforcement along b and h, this is valid for rectangular/square sections, how can have required reinforcement to circular columns?

http://docs.autodesk.com/RSA/2013/ENU/filesROBOT/GUID-84324591-17D9-460E-AF1E-DBD2AF363F8C.htm

When defining R/C member type i've selected nominal curvature to second order analysis...i tried help to get more information but it says page not found...what is happening?

The method follows point 5.8.8 of EC2.

How can i see detailed calculations related to second order analysis...displacements, slenderness and other parameters defined on point 5.8.8 of Eurocode 2 (EN 1992-1-1)?

The detailed calculation note is generated by the RC Column design module only. The RC member required reinforcement does not create it.  

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[RRufino]

The detailed calculation note is generated by the RC Column design module only. The RC member required reinforcement does not create it.

Ok, i experimented that. Is there a way to see the values in table shape or just as calculation note?

[Artur.Kosakowski]

This kind of result is available in the note only.

[RRufino]

Hi again Artur,

I was trying to understand better RC Design looking the values i was talking. But i've some bug on calculation note...

What i'm making:

1. After defining R/C member type i select bar 4 (example)

2. Design -> Provided Reinforcement of RC elements

3. Manual Combinations -> I select just Case 35 (here i don´t understand why othe combinations doesn´t appear, per example combination 26)

4. Select column 4 -> Run calculations

5. I got the warning that column is in tension (that's not possible to combination 35)

6. Looking to "column - note" i see load cases that i haven't selected (case 24/25/26)

7. On point 2.5.1 i see that force are multiplied by -1!? Saying also Conditioning Combination (i don't know if this is text on english version): -1.0026 (A)....what is this?

Model in attachement.

Thanks again

[Artur.Kosakowski]

In addition to selected combination 35 Robot imported also combinations 24, 25 and 26. Please delete them from the load table in the RC Column module before running design of the column.

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.

[RRufino]

I cannot see that table...where can i find it?

How about what i refer on point 3: "Manual Combinations -> I select just Case 35 (here i don´t understand why other combinations doesn´t appear, per example combination 26)"

Thanks

[Artur.Kosakowski]

I cannot see that table...where can i find it?

How about what i refer on point 3: "Manual Combinations -> I select just Case 35 (here i don´t understand why other combinations doesn´t appear, per example combination 26)"

This is currently under investigation but as I wrote they can be easily deleted from the load table of the RC Column module instead.

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[RRufino]

Ok, i already found it.

Regarding point 7: 7. "On point 2.5.1 i see that force are multiplied by -1!? Saying also Conditioning Combination (i don't know if this is text on english version): -1.0026 (A)....what is this?"

I see that robot makes this when load combinations are defined in "nature of case" as seismic...why?

I have other possibilities to nature of case:

- structural (that seems ok)

- non-structural

- category A

(...)

- category H

If nature of case influence column analysis...what is the effect on design for each one of this categories?

P.S.: i kow that category A to cat. H refers to live loads categories on EC2

[Artur.Kosakowski]

Regarding point 7: 7. "On point 2.5.1 i see that force are multiplied by -1!? Saying also Conditioning Combination (i don't know if this is text on english version): -1.0026 (A)....what is this?"

Combination 26 * -1 at the top of the column (point A)

I see that robot makes this when load combinations are defined in "nature of case" as seismic...why?

In general when you define seismic case you usually define it assuming that the excitation is in the positive direction of X or Y but of course in reality it can be in the opposite directions too. This is why they are duplicated and half of them gets -1 factors.

I have other possibilities to nature of case:

- structural (that seems ok)

- non-structural

- category A

(...)

- category H

If nature of case influence column analysis...what is the effect on design for each one of this categories?

They have no influence on the RC Column design.

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[RRufino]

In general when you define seismic case you usually define it assuming that the excitation is in the positive direction of X or Y but of course in reality it can be in the opposite directions too.

True, but already considered on seismic combinations (+-X+-0,3Y and +-0,3X+-1Y)

This is why they are duplicated and half of them gets -1 factors.

Not true to axial forces on seismic combinations.

[Artur.Kosakowski]

Please mind that for vibrations the same point on the structure can move in the opposite directions causing tension or compression. Imagine a simple portal frame with horizontal force applied from left and then from right (structure movement is right - left - right - left ...).

[RRufino]

Right artur, but seismic combinations also have Death and Live Loads, both vertical loads.

You can only think in the way you have in that example to seismic action acting alone...where multiplying axial by -1 is correct. You cannot multiply axial force from vertical loads.

So i'm not seeing the way that this procedure on robot can be correct.

[Artur.Kosakowski · Accepted solution]

I'm afraid this wasn't well communicated from my side. I'll try again in the different way. Imagine a frame as on the picture I attached previously. You define earthquake in the direction X+. Let's assume that only one mode is used and this is the one that causes the structure to move from right to left and back again. This movement (swinging) is repeated number of times (vibrations). The seismic analysis will give you result for let me say max. amplitude of the vibration (in the time history analysis you have many time steps and different level of forces in the elements corresponding to the deformation of the structure at each of these steps) and taht is e.g. when structure moves right just before starting to moving back left. In this point you have compression in the right column and tension in the left one. So the vibrations continue and the structure moves left. Now you have the compression in the left column but tension in the right one. For the designed (e.g. right column) you need to multiply the results obtained for DirX+ case by -1 to include the fact that the frame moves in both directions.

I hope I did better this time.