Masonry wall design

[bjur]

Can robot design masonry shearwalls / bearing walls? There are many masonry structures here in the US and I assume a program this powerful could design structures like this. Do I just create a wall element with similar stiffness properties as a masonry wall? Can robot provide wall stress / loading summeries or do I need to sum forces in the plates by hand?

[Artur.Kosakowski · Accepted solution]

There is no devoted design module for masonry walls available but you can define a panel with corresponding material properties. You can access results in many different ways such as maps or cuts (graphical display) as well as tables (e.g reduced results for panels).

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[Anonymous]

Well, i'm just wondering, is it any option in RSA  to create a structure (in this case,  masonry wall with opening, assume, that reinforced concrete lintel holds all the load), which has no tensile strengh? Thanks very much for your reply.

[Artur.Kosakowski]

No, there is not unless you delete the part over the linter (where you have tension) and 'replace' the weight of this part with load applied directly to the lintel.

[Anonymous]

@Artur.Kosakowski,

is it possible to model plate element with compression stiffness only in defined direction? I think that was original question.
In that way the masonry walls could be obtained.

Regards

Ivan

[Anonymous]

Any new info regarding imatoric question?

[Artur.Kosakowski]

Is this what you mean? 

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[Refaat]

Dear Artur

Greetings

1. Could you find out if I have defined correctly the brick walls as panels have only (compression stiffness) (transfer the slab load to the foundation) or not?
(Please see the capture)

2. Is correct to use the linear release at the boundary of brick walls to prevent any moment transferring between (slab& columns) and brick walls? If so, how do I overcome the instability message (type 1)?
(Please resend the rtd. File after correction)

3. Also, is correct to use a linear support instead of bar (lintel) to avoid any tensile strength in the part of brick wall above this lintel or you have another suggestion ?

Best Regards
Refaat

[Artur.Kosakowski]

Dear Refaat,

I'm afraid that modelling a structure like yours in Robot is difficult. The instability is due to both vertical edges of wall in the corner they meet are released. Perhaps a better choice would be to separate both walls from a column and connect them (if needed) with short bars instead?

I don't think that the lintels can be modeled as supports. 

I'd say the better approach would be to use the load take down approach which used to be available in CBS but is not part of Robot.

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[Refaat]

Dear Artur

Thank you for your response.

The main aim of this modelling to do the structural model for (Masonry building confined with RC beams, tie columns and slabs) as shown in the screen shot.
The brick works will be considered as (Bearing walls) and purpose of these tie RC columns to improve the horizontal and vertical bearing walls capacity (Membrane and shear stiffness of walls) whether gravity or seismic loads But (No flexure).

Could you help me how to do the best modelling for this type of structures?

My attempt as you see in the capture below.

1. Could you verify if I defined correctly the Masonry wall as Bearing wall is or not? Because still I have flexure moments at the corners of these walls. Which shouldn’t be appeared.

2. I would like to define the beams just rested on the bearing walls and its transfer only vertical loads to the bearing walls.

3. How do I defined the lintels where don’t have any tensile stress in the upper part of the wall over it.

Note: for your reference I sent you in (PM) full document concerning this structure type

Also , rtd. File is attached

Best Regards
Refaat

[Artur.Kosakowski]

I'm sorry but I'm not aware of a modelling method of masonry wall with shell type elements which would exactly resemble the way such wall works especially when you want to include lintels. I'd say that typically you just estimate the resultant forces and bending moment acting on such wall (reduced results for panel) and then you design it in the dedicated tool (calculator). 

The other option would be to use the software which analyse the load distribution using the load takedown approach as used to be possible in CBS (see the attached picture).

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[Refaat]

Dear Artur

Thank you for your answer

Actually, I look forward to model concrete structure which its RC beams rested on the masonry walls (Bearing walls) as long as (No transferring moment from RC beam to the masonry wall) and the walls confined with RC columns.

So, the interaction between the RC beams and masonry walls leads to reduce the RC beam size as well the mount of reinforcement for these beams

While as the RC columns increase the horizontal and vertical capacity of these masonry walls.

However, the interaction between the RC members (beams& columns) is very importance in this type of structure.

Please, take a look to the attached (capture and file) to see if I modelled the structure correctly or not?

 Specially, the masonry walls and panel calculation model.

https://www.dropbox.com/s/cjo35rvqlz13dwt/Capture%20%26%20file%20%28Masonry%20structure%20confined%2...

Thank you a lot for your support

Refaat

[Artur.Kosakowski]

Dear Rafaat,

I'm sorry but I find it difficult to tell you this is right or wrong as shell type surface elements as available in Robot are not intended to model masonry behavior. You can see this looking at the bending moment in beams which is zero as the entire load is transferred to the wall below. Perhaps you could consider modelling the linear releases with elasticity for vertical direction and do the same for the horizontal direction for links among the columns and the walls.

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[Refaat]

Dear Artur

Greetings

Thank you for your helpful answer.  I shall have been faster to response.

As you see in the first attached capture. I have tried to keep the required interaction between the frame elements (beam & columns) with the masonry wall by blocking (Uy) once and using the linear release with elasticity as you suggested in another once.

. At the same time I need the masonry wall act as purely membrane element in both direction (x&y). So, I reduced the stiffness coefficients as in the second attached capture.

In both tries still there are slight moments and shears values in the wall. (Third capture)

• May I conclude that the shell element doesn’t represent the real modelling of membrane elements even with stiffness reduction and using the linear release?

• Could I consider what I did the best way to model the masonry wall with RC frame in RSA? Or you have another suggestion.

• Shall I use detailed membrane forces or complex membrane forces in order to compare the results with required design resistance (forth capture)?

• In order to avoid any tension in the part over the lintel shall I use very stiff member? If so, what is the properties of this element?

Note : rtd. file is attached 

Thanks a lot

Refaat

[Artur.Kosakowski]

Dear Refaat,

• May I conclude that the shell element doesn’t represent the real modelling of membrane elements even with stiffness reduction and using the linear release?

Correct. They are not design to behave as masonry. 

I'm sorry but I don't have any additional ideas about modelling this type of walls in Robot in addition to these I already posted and I don't think I'm able to make a better model than yours. The only thing I'd consider is to model a walls without openings and lintels and 'taking care' of them designing a wall separately (e.g. in some calculator) based on reduced forces obtained from Robot.

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[Refaat]

 Dear Artur

Greetings

Thank you for your clear responses.

Eventually, Could you please give me some hints when shall I use ( Principal results and complex results (Mises) because I usually used to read the detailed results only ? e.g. (membrane forces )

Thank you a lot

Refaat

[Artur.Kosakowski]

Principal results

You may be interested in the load transfer (direction) and this is nicely illustrated by crosses (last tab) which correspond to principal stresses (1 and 2). See also:

http://forums.autodesk.com/t5/robot-structural-analysis-forum/q1-2-meaning/m-p/6593531

http://forums.autodesk.com/t5/robot-structural-analysis-forum/plate-principal-moments/m-p/5731517

In addition you have the access to the global and total displacements from there.

complex results (Mises)

Total value of stress in a structure with steel walls e.g. a tank or silo.

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[Refaat]

Dear Artur

Greetings

Thank you to point me to these threads which are explained the theoretical bases of (Principles & complex results). Moreover I have read the help contents related to the same subject.

So, my understanding as following. Please could you review it and correct me?

1. The principle stress value in each principle direction = the stress value in each direction whether (1) or (2)) + (the stress value (12)).

Whereas the crosses represents ((the direction of principle axis of each finite element and the arm length represents the stress magnitude)).

2. Complex value represents the reduced stress value of each finite element which also include the stress value (XY).

Since both of them (Principle & complex) is included plane stress value ((12) &(XY)) respectively .

My inquiry :

Still I am confused  Which one of them (Principle or Complex) shall I used to compare it with the stress design value (e.g. Masonry wall or Concrete wall …etc ) (second capture)?

Or shall I compare the stress design value with the stress value of detailed results for each direction?

Thank you a lot

Refaat

[Refaat]

Dear Artur

Greetings

Please , Could you  help me to get response  ?

Thank you a lot

Refaat

[Artur.Kosakowski]

Or shall I compare the stress design value with the stress value of detailed results for each direction?

IMHO there is no point to look at von Mises stress for masonry and following the changes in the direction of stresses would be not practical so I'd look at the vertical and horizontal directions instead.

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