ETABS Tutorial 14: Understanding Accidental Torsional Effects in ELF and RSA Methods

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@mohammedsmhaan452 11 ай бұрын

thanks you eng. tarek really i am very happy to watch these videos , little videos on internet have an excellent and beneficial information. please keep doing well

@Eng.tarekyoussef 11 ай бұрын

You're welcome! I'm glad to hear that you found the videos helpful and enjoyable.

@ahmadshohibuddaroini8750 11 ай бұрын

Thanks for all ur education videos☺️

@Eng.tarekyoussef 11 ай бұрын

You're welcome!

@ananditonaufalino9567 2 күн бұрын

hi tarek, what table should i display in "display table" menu if i want to know the value of the accidental torsion?

@ViraMustafa 9 ай бұрын

in ASCE 7-22, they have imposed a limitation of using the second approach for RSA in case the TIR (Delta max/ delta avg) is more than 1.6

@Eng.tarekyoussef 8 ай бұрын

The limitation in ASCE 7-22 on using the second approach for RSA when the Torsional Irregularity Ratio (TIR) exceeds 1.6 indicates the importance of considering structural behavior accurately. It's worth noting that the second method, involving physically offsetting the mass, could potentially amplify the effects of accidental torsion for some buildings with torsional first modes. In my opinion, engineers should not adopt any approach blindly. They need to conduct a thorough investigation to determine which approach is more logical and accurately predicts the real response of the structure.

@ronykhadra3173 8 ай бұрын

@@Eng.tarekyoussef if TIR exceeds 1,6 and a RSA is required, i think that it is ok to compute the Ax from the ELF procedure and then override the eccentricities in the response spectrum; however, this would require defining U1 and U2 as 2 separate load cases to be able to assign eccentricites for each direction, where applicable; Then, in the combinations, we can use 100% of one direction and 30% of the other; this is not very much recommended since it is better to use U1 and U2 in the same load case so the structure will be oscillated in the principal axis; so whatever we do has its limitations

@DesignNexus24 10 ай бұрын

Thanks for this usefull tutorial

@Eng.tarekyoussef 8 ай бұрын

You're welcome. Glad it was helpful

@ViraMustafa 9 ай бұрын

if our Ax value comes out to be more than 3 (lets say 4) then do we need to change our structural system in order to reduce the Ax value or should we just take it 3 and design accordingly?

@Eng.tarekyoussef 8 ай бұрын

When the Ax value exceeds 3, it means the structure is at risk of instability due to torsional forces. To ensure safety, it's crucial to follow code requirements closely. If Ax is too high, structural changes are needed to reduce torsional effects and maintain stability.

@elenajivkova1308 8 ай бұрын

Thanks a lot for everything. Are you thinking of continuing?

@Eng.tarekyoussef 8 ай бұрын

Yes, soon

@ahmedtalib717 8 ай бұрын

Hi, Tarak .. Did you have the updated Excel file to include the ACSE7-16 in your axel sheet? since the value of the Fa and Fv are changed?

@Eng.tarekyoussef 8 ай бұрын

Hello Ahmad. Not yet updated to ASCE 7-16. I am using ASCE 7-10 in my excel sheets.

@fazilpatel8723 11 ай бұрын

Please share Excel. Also, can you also do a full video with an example design of multiple towers in a building in ETABS?

@Eng.tarekyoussef 10 ай бұрын

drive.google.com/drive/folders/1WWyrqs8OaJbvIjkEqigb8ki_FDQmfauO?usp=sharing

@ananditonaufalino9567 2 ай бұрын

hi tarek, if the results based on using the second technique showing that the ratio still exceed 1,2 and come out with the torsional irregularity 1a or 1b, what should i do based on the final results to determine the accidental torsion if the Ax can't be used if i'm using second technique?

@Eng.tarekyoussef 2 ай бұрын

Hello, If you're using the second technique, which involves shifting the center of mass using the modal load case, you don't need to calculate the Ax factor (this factor amplifies eccentricity), because the effect of shifting the center of mass is already included in the analysis. However, the Ax factor can still provide insight into how much the structure would rotate if the center of mass were shifted. If you find that the Ax factor is notably high, approaching 3, I advice you to modify your structural configuration to mitigate these torsional effects and enhance stability.

@anandito6833 Ай бұрын

@@Eng.tarekyoussef thankyou tarek, and then why did we must change the load case type to nonlinear static? since the approach of RSA method is the linear dynamic analysis method?thankyou

@Eng.tarekyoussef Ай бұрын

@@anandito6833 we need to define the nonlinear static load case to be able to add a new modal load case. Please note that for RSA method, the type of load case defined is Response spectrum and not nonlinear static.

@คณิศรปิยะตระภูมิ 8 ай бұрын

Torsion amplification should late in the same time of p delta effect or not Thank you

@Eng.tarekyoussef 8 ай бұрын

In my opinion, examining torsion amplification after incorporating the P-Delta effect in the analytical model is the optimal approach. The P-Delta effect accounts for the geometric nonlinearity caused by the interaction between axial loads and lateral displacements. Once this effect is considered, assessing torsion amplification becomes relevant as it captures how lateral displacements induce additional torsional moments, particularly in asymmetric or eccentrically loaded structures. By addressing the P-Delta effect first, the analytical model can provide a more comprehensive understanding of the structure's behavior under lateral loads, including torsional responses.