Introduction to Seismic Analysis through a Case Study of Irregular Multi-Tower Buildings

[@tersorakoso4702]

The master is back. I always reference your videos. Great content.

[@khalilothman5638]

Big Support , Hope to see more dynamic NL analysis

[@melkamuataro7858]

Well back & Keep it up!!!!

[@karzankamal9402]

Thank you, Mr. Tarek. Excellent illustration-could you upload the file?

[@user-qu2tj6ih5z]

جزاك الله خير بش مهندس طارق وممكن ترفع لنا ملف الشرح لنتابع معاك وشكرا

[@kebzkebz3110]

Hi Sir! I wish to know how to include the SF x OmegaO / R in the 1st mode Base Shear, how can we do this in ETABS?

[@Eng.tarekyoussef]

Hello! In the MRSA-HE approach, you enhance the first mode by scaling it with SF*Omega/R. This adjusts the modal acceleration of the first mode by modifying the spectrum. The process involves: 1. Modal Analysis: Conduct a modal analysis to find natural frequencies, mode shapes, and modal damping ratios. 2. First Mode Identification: Identify the dominant first mode for both X and Y directions, which significantly contributes to the structural response. 3. Scaling Factor Calculation: Calculate the scaling factor (SF) as 0.85*VELF/VRSA, where VELF is the base shear from the equivalent lateral force procedure, and VRSA is the reduced base shear by I/R of the response spectrum analysis method. Then compute the first mode's scaling term as SF*Omega/R. 4. Spectrum Adjustment: Modify the spectrum by multiplying the acceleration of the first mode with the term SF*Omega/R.

[@ChristianLegrandOliva-hj9je]

Hello engineer, all your tutorials are very good, I wonder if you get more tutorials from this study, as a step by step to reach the same results.

[@Eng.tarekyoussef]

I'm happy to know that you find my tutorials helpful I'm currently working on making more tutorials that will guide you step by step through a study like the one you're interested in. Even though the building in these tutorials may not be exactly the same as the one you're asking about, the methods and techniques I'll be explaining are the same and can be applied to any structure. Right now, I'm focused on creating videos for the ETABS software, and you can find them in a playlist called "ETABS Course 2." I also have plans to create tutorials for Perform 3D software in the near future. Stay tuned for more helpful content that will assist you in achieving similar results in your study.

[@aldiputra9236]

How to applying the seismic load if our building rotation from global axis etabs sir..thank because seismic way follow global axis actually..

[@Eng.tarekyoussef]

In the seismic load definition, specify the direction of the seismic load. Since the seismic load follows the global axis, you should align the seismic load direction with the global axis of your structure.

[@rjkebz312]

Hi Sir!, may we know how to do the Scale Factors in ETABS using the MRSA-HE? thank you in advance

[@Eng.tarekyoussef]

Hello! In the MRSA-HE approach, you enhance the first mode by scaling it with SF*Omega/R. This adjusts the modal acceleration of the first mode by modifying the spectrum. The process involves: 1. Modal Analysis: Conduct a modal analysis to find natural frequencies, mode shapes, and modal damping ratios. 2. First Mode Identification: Identify the dominant first mode for both X and Y directions, which significantly contributes to the structural response. 3. Scaling Factor Calculation: Calculate the scaling factor (SF) as 0.85*VELF/VRSA, where VELF is the base shear from the equivalent lateral force procedure, and VRSA is the reduced base shear by I/R of the response spectrum analysis method. Then compute the first mode's scaling term as SF*Omega/R. 4. Spectrum Adjustment: Modify the spectrum by multiplying the acceleration of the first mode with the term SF*Omega/R.

[@rjkebz312]

@@Eng.tarekyoussef Thank you very much sir for your prompt reply! May I clarify 3 things: #1. for item 3, which modes shall we consider in the calculation of VRSA? is it the dominant mode only for each direction (1 in X and 1 in Y)? #2. for item 4, does the Spectrum Adjustment means we are going to use 2 Adjusted Spectra to be used since we have 2 dominant modes, 1 for X direction and 1 for Y direction? #3. for item 3, may I clarify if the R factor to be used in SF*Omega/R comes from Pushover Analysis?

[@Eng.tarekyoussef]

@rjkebz312 1- In MRSA-HE, it's crucial to combine all vibration modes to obtain the total response. For instance, if we use 15 vibration modes (giving over 90% mass participation), each mode consists of 2 translational components and 1 rotational component. This means a mode can purely translate in one direction, exhibit coupling between UX and UY, or even involve all three components. Therefore, selecting the mode with the highest participation in a given direction (typically the first or second mode) is essential. However, for the final results, we must combine all modes, including those not participating in that direction and with the adjustment of the first mode selected for that direction. 2- Yes, we indeed require 2 spectra for each direction, with each spectrum being adjusted to the first fundamental mode of its respective direction. 3- In MRSA-HE, we utilize the "R" factor specified in the design (obtained from ASCE). For MRSA-HI, a pushover analysis is necessary to calculate the R factor.

[@rjkebz312]

@@Eng.tarekyoussef Thank you very much sir! I hope to learn more from your channel.

[@aliwael8126]

how do you compute T for each building in the same etabs file ?!

[@Eng.tarekyoussef]

I am not entirely sure if I understand your question, but for this study, I have used two buildings: SH and DH. These buildings were designed for two different locations in Thailand: Bangkok and Chiang Mai. Consequently, I have created a total of four ETABS models, with two models for each location. Therefore, I have obtained the modal properties of the buildings (natural periods, natural frequencies, etc.) using the ETABS models I created for each location.

[@aliwael8126]

​@@Eng.tarekyoussef Each building containing 2 towers with connected podium in lower stories when designing each tower should i study each tower separeatly or all the building in the same model ?? What if i have a 4 stories basement ? how i can scaling the base shear at ground !? what if the stiffness to the two tower are diffrante ?!

[@Eng.tarekyoussef]

There are two main approaches to consider when designing a building complex with two towers and a connected podium: 1. Separate Tower Analysis: Study each tower as an individual structure, but remember to provide expansion joints between the podium and towers during construction. 2. Integrated Building Analysis: Model the entire building complex as a single structure. This approach considers the interaction between the towers and the podium from the beginning, providing a comprehensive understanding of the building's behavior. In my case study, I used option 2 because it allows for a better understanding of the interaction between the towers and the podium right from the start. However, in practice, option 1 (Separate Tower Analysis) is often more preferred. For the 4-story basement, it's worth noting that, according to my knowledge, the basement's weight is typically not considered in seismic analysis. However, it is essential to check your local building code to ensure compliance with the recommended practices. Additionally, keep in mind that if the stiffness of the two towers differs, it will affect the distribution of lateral forces during seismic events. The stiffer tower will attract more lateral force, while the less stiff tower will experience a smaller portion of the force. Therefore, it's crucial to carefully assess the stiffness of each tower and how it impacts the overall behavior of the building complex.

[@prajwalaavarebeel1790]

When we have a expansion joint, it is preferable to do separate models rights. Or will it right to model them as multi tower ?

[@aliwael8126]

I Talk about no expansion joint case @@prajwalaavarebeel1790