Shear directions and center of stiffness

[iek58]

hello, we have two floors of basement as seen in the photo below. In the basement 2, which is the lowest floor, there is a soil load on both sides, so curtains are needed on both sides. In the basement 1, which is an upper floor, a curtain is needed only on one side, the ratio of the short side to the long side is 1/4, so the stiffness deviates a lot. rigidity is not calculated. this actually works for me, however, the curtains defined as the inundation at the time of the earthquake do not say "I am the inundation curtain. I do not take any load on me". changes the rigidity as well. Our Center of Rigidity is moving away from the Center of Mass (assuming it is at the building centre) because the curtain length is too long on one side. hence the torsional effects increase. What are your comments in this situation?

 

[HakanŞahin]

when we design these curtains as basements, they are not included in the calculation of alfaS, but the stiffness is not calculated. This actually works for me?

This statement is not correct. You should mark the curtains you entered as basement or not, they are in the system and cannot be analyzed. Therefore, they affect the location of the center of rigidity. The fact that the sub-basement walls are not included in the calculation of AlfaS is another issue. Since those walls are not included in the calculation of alfas, they are not included in the calculation of alfas. The sub-basement walls affect the center of rigidity and dynamic behavior of the building.

 

[MaFiAMaX]

Hakan has also stated that whether you mark a curtain as a basement or not does not change the dynamic behavior of the building. That is, the center of stiffness of the structure and the earthquake force to be calculated (independent of Ra) are the same. While calculating the earthquake load reduction coefficient Ra, we use the structural system response coefficient R. In the R calculation, we first select the value that is appropriate for the building system from the table and start the analysis. Then we calculate alpha-s and calculate the real R value, and therefore Ra. The approach of the regulation in the calculation of alpha-s is the ratio of shear shear forces to the total base shear force. Here; 1-) If there is a rigid basement floor, we are told to calculate the total shear force of the curtains on the floor immediately after the basement and to compare it to the total shear force in that floor. If one side of the basement floor is closed with curtains, it is considered as rigid, but if one or more facades do not have curtains, it is not said what to do. For this reason, it is very clearly explained how to decide this in the new regulation

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[iek58]

Hakan Bey also stated that whether you mark a shear wall as a sub-basement or not does not change the dynamic behavior of the structure. That is, the center of rigidity of the structure and the earthquake force to be calculated (independent of Ra) are the same. While calculating the earthquake load reduction coefficient Ra, the carrier We use the system behavior coefficient R. In the calculation of R, we first select the value suitable for the building system from the table and start the analysis. Then we make the alpha-s calculation and calculate the real value of R and therefore Ra. The approach of the regulation in the calculation of alpha-s is the total base shear force of the curtain shear forces Here; 1-) If there is a rigid basement floor, we are told to calculate the total shear force of the curtains on the floor right after the basement floor and to proportion it to the total shear force in that floor again. If the basement floor is closed with curtains on one side, it is considered as rigid, but one or more It is not said what to do if there are no curtains on many fronts. However, it is very clearly explained how to decide this

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2-) We are told not to take into account the curtains that do not protrude throughout the building and do not act as the main curtain of the building, even if they are not in the rigid basement floor, while summing the shear forces. After you mark the floors you want to be a rigid basement in the ideCAD floor settings, if there is a curtain that you do not want to be included in the alpha-s calculation on a normal floor, we enter that curtain properties and mark it as "subbasement curtain". "Thanks to you, I learned that my opinion was wrong. In order for me to accept rigid direction in the program, as far as I understand from the relevant article (a) of the regulation, I need to surround it with curtains from 3 sides on both floors. is it correct ? respects

 

[MaFiAMaX]

I learned that my thought that "floor bulkheads are not included in the calculation of stiffness" is wrong, thanks to you, I need to surround it with curtains from 3 sides on both floors, as I understand from the relevant article of the regulation, in order to accept rigid direction in the program. Regards

There is no such definition in the current regulation, but in general, you can stipulate that at least 3 facades must be closed with curtains.Of course, if someone inspecting tells you that if the entire facade is closed with curtains, I would accept a rigid basement floor, it would be more than convincing. The regulation that I showed you the image of is not in effect yet.

 

[iek58]

I learned that my opinion that "floor bulkheads are not included in the calculation of rigidity" was wrong, thanks to you, in order for me to accept rigid direction in the program, as far as I understand from the relevant article (a) of the regulation, there are two floors. I need to surround it with curtains from 3 sides. is it correct ? Regards

There is no such definition in the current regulation, but in general, you can stipulate that at least 3 facades should be closed with curtains. Of course, if someone inspector says to you that I would accept a rigid basement if the entire facade is covered with curtains, you have no choice but to convince him. The regulation that I showed you the image of is not in effect yet.

thanks, 70 needs to be done in basement 2 (40+15) 70 needs to be done in basement 1, 70 needs to be done in basement 1, and we are doing these only to carry the soil load. it's hard to explain this to contractors