Excess Of Shear Walls Causing Probelms

[abdulqadeer29]

i have an issue to discuss, regarding my etab and safe model... My etab model is good upto my knwledge AS I HAVE CHECK LOAD COMBINATIONS AND OTHER RESPECTIVE THINGS NEEDED TO BE CHECK, when i come to safe , due to few load combos having earthquake factor i got lot of moments specially in areas having shear walls so kindly tell me when we design foundation, do we have to consider all these load combos and how to avoid large reinforcement which is coming in areas of shear wall bcoz i thnk so practically so much reinforcement is not possible...\
I HAVE MODELED MY SHEAR WALLS AS PIN BUT NOT YET SATISFIED WITH MY RESULTS...
building sizie is 90x180 so almost double in other direction and total no of storeys is 15...i used col size 15x36 , so need ur suggestions??????????

try 3.zip

[Waqar Saleem]

for foundation only service load combo should be checked not the all load combinations.in your model in load static cases there is no wind load taken your building is 15 storeys so wind load must be included,in load cases in EQ loads bottom story is 2story,is it ok ?or it should be lowest story.

[UmarMakhzumi]

 i have an issue to discuss, regarding my etab and safe model... My etab model is good upto my knwledge AS I HAVE CHECK LOAD COMBINATIONS AND OTHER RESPECTIVE THINGS NEEDED  TO BE CHECK,  when i come to safe , due to few load combos having earthquake factor i got lot of moments specially in areas having shear walls so kindly tell me when we design foundation, do we have to consider all these load combos and how to avoid large reinforcement which is coming in areas of shear wall  bcoz i thnk so practically so much reinforcement is not possible...\

I HAVE MODELED MY SHEAR WALLS AS PIN BUT NOT YET SATISFIED WITH MY RESULTS...

building sizie is 90x180 so almost double in other direction and total no of storeys is 15...i used col size 15x36 , so need ur suggestions??????????

Can't open up the zip file ? @Waqar, he might be doing that becuase of the basement.

[abdulqadeer29]

Can't open up the zip file ? @Waqar, he might be doing that becuase of the basement.

 i am attaching again...

try 3.zip

[abdulqadeer29]

for foundation only service load combo should be checked not the all load combinations.in your model in load static cases there is no wind load taken your building is 15 storeys so wind load must be included,in load cases in EQ loads bottom story is 2story,is it ok ?or it should be lowest story.

i have a question...should we deisgn a strcture for both seismic and wind...when that strcture is more likely to be critical with respect to seismic not wind....

[Waqar Saleem]

when there are both EQ and Wind ,above 8storey or 80ft height wind is governing in most of the cases.

[UmarMakhzumi]

 i am attaching again...

See the attached image. Is your system clean? The only thing that comes to my mind is that my AV doesn't let it open. I cann't turn it off as I am at work.

 

You should always design your structures for every possible limit state. Unless you "calculate" both wind and seismic, you cann't ignore any load & there is no thumb rule to include or exculde wind or seismic as both depend on different parameters. For the sake of argument, if we say that seismic controls for a high category tall buildings, you will be surprised that some members in your structure would be goverened by wind. So do both.

 

Please post your summary output file from Etabs.

[Ayesha]

i have a question...should we deisgn a strcture for both seismic and wind...when that strcture is more likely to be critical with respect to seismic not wind....

I cannot get hold of your attachment too. I noticed that you can also upload ETABS edb and $et files.

[UmarMakhzumi]

I cannot get hold of your attachment too. I noticed that you can also upload ETABS edb and $et files.

Yes, you can upload in these formats.

[abdulqadeer29]

check these otherwise i will try sthng else.....

try 3.$ET

try 3.zip

[abdulqadeer29]

one more effort ....myt be helpful.....

try 3.$ET

Etab model.zip

[asadishaq]

Is this the correct way,of modelling beams over shear wallls???

[UmarMakhzumi]

Is this the correct way,of modelling beams over shear wallls???

I would not. Should be modelled as spandrels.  Plus I would not use columns at end of walls too.

For me, the bad thing is that I don't have access to Etabs anymore. Here in my office, I can only use SAP2000 and Risa3d. I thought I could import the $et file but looks like you need a seperate file to export from ETABS for SAP2000. Anyways, as posted above by AQ, the building is wide spread, and making cores shear walls would end up drawing more torsion.

 

AQ:

Can you please upload framing, showing what column sizes you are using?

 

Thanks.

[abdulqadeer29]

  i usually prefer line load on beams instead of partition load on slabs.

i have applied these loading in current model....

live load for residential 40 psf

live load for corridors and stair area 100 psf or 80 psf

live load for parking area 100 psf

Sdead 56 psf 

Line load on beams 600 lb per linear foot 

now someone suggest me that i should go for partition load on slab not line load on beam so i need anyone's comment on this one??????

[UmarMakhzumi]

  i usually prefer line load on beams instead of partition load on slabs.

i have applied these loading in current model....

live load for residential 40 psf

live load for corridors and stair area 100 psf or 80 psf

live load for parking area 100 psf

Sdead 56 psf 

Line load on beams 600 lb per linear foot 

now someone suggest me that i should go for partition load on slab not line load on beam so i need anyone's comment on this one??????

Line loads are better than slabs. You don't really need to model slabs. Just assign all kind of loading and diaphragms manually.

Have you meshed your walls? From the image posted above by asadishaq, I can see that they aren't. And that is infact 1 reason you are having very high reactions under shear walls, as loads are concetrated at two points just under walls, where, infact there should be quiet 'linear'. Do that, and we will look at the next step.

 

[abdulqadeer29]

Line loads are better than slabs. You don't really need to model slabs. Just assign all kind of loading and diaphragms manually.

Have you meshed your walls? From the image posted above by asadishaq, I can see that they aren't. And that is infact 1 reason you are having very high reactions under shear walls, as loads are concetrated at two points just under walls, where, infact there should be quiet 'linear'. Do that, and we will look at the next step.

yoy are right , i didn't mesh walls.....that myt be the reason of getting high reactions under shear walls.....okay i will do this and then vl share my results ... 

[abdulqadeer29]

I would not. Should be modelled as spandrels.  Plus I would not use columns at end of walls too.

 

 

 

What do you mean by Spanderal, ??? What i understand is this (shown in figure) , make me correct i am going the other way.........

[Ayesha]

See the attached image.

[asadishaq]

Your shear walls and beams are overlapping.why you are modelling beams over shear walls.

[Shahbaz Bangish]

abdul qadeer 06 should upload your framing in pdf format so that we can comment and do markups. Just an idea.

[abdulqadeer29]

abdul qadeer 06 should upload your framing in pdf format so that we can comment and do markups. Just an idea.

here is my framing plan...

frame Layout1 (1).pdf

[abdulqadeer29]

Line loads are better than slabs. You don't really need to model slabs. Just assign all kind of loading and diaphragms manually.

Have you meshed your walls? From the image posted above by asadishaq, I can see that they aren't. And that is infact 1 reason you are having very high reactions under shear walls, as loads are concetrated at two points just under walls, where, infact there should be quiet 'linear'. Do that, and we will look at the next step.

i Got a more reasonable results after doing meshing of walls ....now i want to modify my model by placing minimum number of shear walls , to control deflection of building....

now my question is should we observe a couple behavior( equal number of shear walls on both sides, but i have a limitation that at one side it would be impossible for me to palce a shear wall of length geater than 10 feet due to dive way at basement) when we are placing shearwalls???

[Ayesha]

i Got a more reasonable results after doing meshing of walls ....now i want to modify my model by placing minimum number of shear walls , to control deflection of building....

now my question is should we observe a couple behavior( equal number of shear walls on both sides, but i have a limitation that at one side it would be impossible for me to palce a shear wall of length geater than 10 feet due to dive way at basement) when we are placing shearwalls???

 

What are your column and beam sizes ? What other options did you come up with framing ? By how much are your numbers off a stable design ?

[UmarMakhzumi]

i Got a more reasonable results after doing meshing of walls ....now i want to modify my model by placing minimum number of shear walls , to control deflection of building....

now my question is should we observe a couple behavior( equal number of shear walls on both sides, but i have a limitation that at one side it would be impossible for me to palce a shear wall of length geater than 10 feet due to dive way at basement) when we are placing shearwalls???

Delete columns at the end of your shear walls and your results would become even. Check your building for torsion irregularity and drifts. You cannot always have a symmetric framing.