Load takedown on floating columns

[Djokaboris]

Hi;

Just from doing the loadtakedown on column in RSA, and why do RSA doesn't take into account the floating columns and many others columns during the load takedown?. Even for the corner columns, the moment(M)  is not taken into accounts. I'm i right or there's a workaround to get this result. Need a hand in this 🙏.

[okapawal · Accepted solution]

Hi @Djokaboris 

Load Take-Down is a simplified method which simulates transfer of the vertical loads down to foundation.  It does not generate moments on columns.

[Djokaboris]

Yeah Sir @okapawal i understand, but i wonder why it doesn't take into account the axial loads from level2-4.  robot doesn't take into account the load takedown and distribute axial load in floating columns structures or am i mistaken. And why is it that in the structure there are not axial load from load takedown in most of the column. I understand that sometimes there might be RC tension column that doesn't receive any load, but not for almost all the structures like that

[okapawal · Accepted solution]

@Djokaboris 

Actually, in both attached examples you are using regular FE method, not the Load Take-Down.

Pay attention that beams and columns are not connected at some points.

You may run Edit > Correct Drawing Model..  command to make coherent model.

at least with 10 cm tolerance.

[Djokaboris]

Thanks for your answers sir @okapawal ,  the overlaps found by RSA when using shells are only due to beam supported by beams. i used a precision of 10cm but still columns from level 3 and 4 don't receive  normal force(N) after load takedown. 

[Stephane.kapetanovic · Accepted solution]

hi @Djokaboris 

overlap members

Extend 155to158 225to228 405to408 493 508 510 beams to 154 224 351

split column

Best Regards

[Djokaboris]

Thanks sir @Stephane.kapetanovic , did the correction, but the only warning right now is instability type3 that i'm unable to detect. Did load takedown but still no compressive load on a lot of columns

[Djokaboris]

Finaly work the whole day on the error and corrections. Thanks Sir @Stephane.kapetanovic , Sir @okapawal  ,this is an updated structure with no errors but still a lot of columns don't have compressive load during load takedown. Don't get why RSA does that

[Stephane.kapetanovic · Accepted solution]

hi @Djokaboris 

you should orient the panel axes so that the mesh is aligned with the main axes of the structure.

wall 705 and corners of 608 & 752 are not planar with the floor rows and cut-outs. you need to change the coordinates to x=37.863531494 and y=-10.593915721.

You haven't finished the sizing and the detailed analysis of the structure, so I won't comment on your work and leave you to get on with it.

apart from working on the proportions of columns, beams, walls and slabs, the structure will not be re-analyzed.

Remarks :

deflexion of beam 89 seems to big (4.7cm DL only). it is possible to directly increase the height of the beam (0.3>1.20m) to continue looking at the behavior of the structure and not dwell on the misunderstanding it may induce.

there are posts that you can orientate according to their frame (inclined) to benefit from all their inertia.

after that, it's possible that some columns are subject to tension (454 for example), but this is mainly due to the frame system in which they operate.

you should read the EXP report

report deleted

Best Regards

[Djokaboris]

Thanks a lot for the corrections Sir @Stephane.kapetanovic , my apologies for my lateness, was actually working on the file.

 noticed there's a high deflection on the slab above , and  columns can't actually be placed because there's a conference room at the base. 

The high deflection of 50m  is at the  slab of 10x11m and the pedestrian bridge. Normally in the execution process i think we usually do rib or waffle slab but when applying theses slab, the deflection does decrease only by 2mm.

As for beams increasing the beam depth icreases the weight of the slabs which increases the deflection as from the result i get

Please how can we decrease this high slab deflection in RSA?

[Stephane.kapetanovic · Accepted solution]

HI @Djokaboris 

The deformation is 50mm, which can be explained by the constructive choices and design constraints that you share responsibility for with the architect, both functionally and mechanically.

Please review your mesh again to ensure it is harmonious and resolve any remaining error messages. As explained, you need to carry out a sizing step, eliminating anything that is not robust and economical. If the project becomes unfeasible with your current means of implementation, you will, of course, need to explore alternative load transfer methods.

Once you have done this, you will be in a much better position to address the remaining critical points.

Best Regards

Report deleted

[...]

[Simau · Accepted solution]

Hi @Djokaboris 

A small correction to your model:
- I splitted the columns and interior walls at stories level for a better
- I remesshed the panels
You said: "As for beams increasing the beam depth i creases the weight of the slabs which increases the deflection as from the result i get". This is not my case as i reduced the deflection to 27 mm with 300x900 beams.

In fact you used 300x300 beams which is insuffiant for span of 7 to 10 m.

Why did you use only 300x300 beams for all the stucture?

Model attached

[Djokaboris]

Hi Sir @Simau ;

My apologies for the late reply. Doing the manual calculations of columns all this time.

Many thanks for your responds and help Sir @Simau . Was totally wrong about the deflection increase after beam Sizing.

Please how did you split the columns by stories. Because i can't find this option in edit>>division.

and still  there problem of provided reinforcement of RC slab in Robot. haven't  still find out why nothing is displaying in this option .

[Stephane.kapetanovic · Accepted solution]

hi @Djokaboris 

you can divide bars by plane

you can also use "Cut by Plane" option for objects. [1], [2]

Best Regards

[Djokaboris]

Hi Sir @Stephane.kapetanovic ;

Robot recognize that it's split but still select the entire shear wall.

[Stephane.kapetanovic · Accepted solution]

probably meshed but not split. use second method (cut by plane - split object - plan XY + select level)

[Simau · Accepted solution]

Hi @Djokaboris 

It's better not to split these 3 walls as they are not intercepted by any floor

[Djokaboris]

Yeah i know Sir @Simau , it was just a test. 

I sized and design a column. But when including fire provision errors bulges. It's due to my effective length>3  and the e>emax theoritically.

But please how can we design for this fire provision of 1hr  in robot? 

[Simau · Accepted solution]

Hi @Djokaboris 

Before focusing on fire provision, please make sur your structure is well designed. For example here some comments:

Huge displacements under EP load

Using only 300x300 for near all beams and columns although there is span from 10 m to 13 m

High heigt (16 m) for some walls

Strange value for EP load

EP load applyed only in one side of the basements.

No walls in part of the basement

[Djokaboris]

Hi Sir @Simau 

The huge displacement is caused by no supports on the elevator. Just from inserting it Sir.

For the beams and columns, i don't have problems with it because i can easily size and design it in the RC design GUI without errors.

But have a lot of errors when designing a raft foundation design and slab design. Can i get a hand  with this problem please??