Torsion Detection

[berkehan]

Hello there. I would like to get your opinions on a situation we encountered in our project. 1-) When I play the model with no curtain in the Y direction and the model with a curtain in the 3D frame while in Modal E1 mode, I see that the model with the curtain is twisted and the model with the curtain is oscillating normally. The curtain does not center the building exactly in the Y direction. There are also modal E1, E2, E3, E4, BE1, BE2, BE3 and BE4 options. What is the difference between these options, from which one should we understand whether it is the first torsion? I would like those who had the chance to examine the models to give their opinions on which of the two models we should apply. 2-) I am also getting an error (N) in the short span beam that is rigidly connected to two curtains in the basement. Rigidity reduction, definition of freedom etc didn't work. I would like to know your suggestions about the solution.

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[Ismail Hakki Besler]

The first mode of your fretted model is torsion, and the fretless one's first mode is not torsion, but the second mode is torsion. Although the individual modes have a meaning in dynamic analysis, the most important thing is the combined response values. Already in this combination, the values that come out due to the high period of the torsion mode and the contribution margin penalize the structure. If there are curtains in your structure, you will naturally enter the curtains. In addition, you need to solve this type of structures with scattered masses as if there are three separate floors (Buildings) on each floor, semi-rigidly. Thus, you can also examine plan irregularities.

Modal E1, E2, E3, E4, BE1, BE2, BE3 and BE4 options are also available. What is the difference between these options,

These are not options, All these dynamic calculations are done together and the envelope is used. This is a requirement of the earthquake code.

How should we understand whether it is the first torsion?

If the first mode in the structure is torsion, you will see this mode in all dynamic analyzes with shifted masses (E1 E2 E3 E4 ). It is selected from the menu below. It is not against the regulation that the first mode is torsion. It will only produce more unfavorable results and you cannot cope with optimizing the structure, especially on bad ground.

 

[berkehan]

It is in our hands whether there are curtains in the building or not. If it causes problems because the curtain is not in a suitable position, we will turn it into a beam and design the structure without curtain in Y direction. However, I would like to do this not because the quantity of concrete/reinforcement increases, but if it is healthier. I think it would be healthier to remove the curtain that causes more unfavorable results due to torsion in the 1st mode, because it is caused by the behavior of the structure. Correct me if I'm wrong please.

 

[Ismail Hakki Besler]

The curtains that are not well associated with the building are like the curtains of the neighboring parcel. In this case, the curtains do not have a direct diaphragm connection. It is better not to enter.

 

[berkehan]

The curtains that are not well associated with the building are like the curtains of the neighboring parcel. In this case, the curtains do not have a direct diaphragm connection. It is better not to enter.

Your opinion is important. Thank you very much.