Designof a tank - Effect of gusset on reinforcement

[genieyas]

Hello every body,

i have to design a tank, first a take a husset of 45cm, then i calculate my tank, the reinforcement along Y+ is 6.38cm2/ml

In the second model, i take a gusset of 65cm!!!, i was surprised by this result because increasing the section on concrete means increasing the amount of reinforcement, i found Y+: 7.63cm2/ml

Could some one please help me to undersood this? attached the too models.

[genieyas]

[Stephane.kapetanovic]

hi @genieyas 

The problem may not be this, but look at this steel example

Best regards

[Stephane.kapetanovic]

[genieyas]

Hello

Think you for your answer

but how could you explain that the lowest bending moment in fiste case gives the greatest stress (your second response)?

I can understand that for hyperstatic structure the most rigid the element is the most it take of bending...

But how can i explain the utimity of gusset in reinforcement concrete, as i know, if we add a gusset so the section of concrete increase, then automaticly the amount of reinforcement decrease...

But unfortunately, this logic idea i have aboit guesset is not true in RSA!!!!!

Could you help me arrange my understanding

thinh you very much

[genieyas]

Hello,

I think you are right, in your case (steel model) the stress in steel drop down because of the existing of gusset (hight of section bigger), you are right.

But in concrete reinforcement, We calculate steel amounth dircetly from Bending moment.

So i think that, in concrete reinforcement, Gusset only reduce stree in concrete but dos'nt impcat reinforcement, it is likly true?

Sincerly

[Stephane.kapetanovic]

hi @genieyas 

First of all, what I wanted to explain was the progression of the bending moment. In a second hand, the stresses are lower due to the height of the section.

It also seems to me that the distance between the compressed concrete zone and the tensioned steel is favorably changing also in your case. Could you make sure by making cuts that the proportion is in your favor and that the other walls are not overloaded too ?

Best Regards

[StefanoPasquini6790]

dear @genieyas ,

the reinforcement area is not calculated only with the bending moment, but it have to respect the criterion of the minimal area due to the volume of concrete, so if you increase the height of the plate, even if the bending moment decrease, you'll have an increment of reinforcement area.

Try to run this test, model a square plate, apply the same load for them and run the calculation, you will reach the result as reported here:

MOdelApplied loadsBending momentReinforcement areas

[genieyas]

Hello

Think you for your answer

You are totaly right, there is minimum reinforcement according to the section of concrete (fragility condition)

If we return to my exemple of gusset:

- How could i optimise reinforcement using the gusset where bending moment is big (fixed bord of pannel)?

- If the gusset will increase the amount of reinforcement, i prefer not to use it, but it is usully used in this kind of ouvrage, so what is the purpose of it?

Sincerly

[StefanoPasquini6790 · Accepted solution]

Hi @genieyas ,

gusset help RC elements to reduce punching effects, increase rigidity and reduce the displacements.

In one of my recent project, I used rigid links to model gussets, and to avoid bad calculation of reinforcement. The project was a University Research Building, seismically isolated, with a push machine to simulate the quake on the building. The gusset wall received a push force of 10.000 KN, and the response was very good.

The following picture it show the Robot model

And the following video it show the push test done last year over the building, where you can see also the gussets

https://www.youtube.com/watch?v=6kg7rg9W0ck

Hope I help you, cheers