Seismic Analysis of Multi-Story Buildings using the Response Spectrum Method
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- Опубликовано: 1 авг 2024
- In this video, the use of Response Spectrum analysis in seismic analysis and design of Multistory Buildings is explained.
The free vibration of Multi-story buildings is explained along with the concept of mode shapes.
The method of modal analysis is briefly explained. In a modal analysis the multistory Mutli-Degrees of freedom (MDOF) building is
converted to a number of single degree of freedom (SDOF) Structures.
Then it is shown how to use the modal analysis method to find the seismic forces using the response spectrum curve.
An example is given on how to analyze a Multi-Story MDOF system using ASCE7-10 Response Spectrum method.
Although the lecture uses specific factors and provisions from the ASCE-10 Code, most of the procedure is valid for any other design code.
For More information on response spectrum analysis watch the following lecture:
• What is a Response Spe...
For More information on the principles of dynamic analysis, watch the following lecture:
• Dynamic Analysis of St...
Wow... this lecture is very excellent.. you answer me about many question in my mind .think you professor and please continuous like these topic.
Hello Sir, really want to express gratitude for this video, its amazing that in 30 minutes we feel so confident and energetic of this Spectrum concept which had always been revolving on top of the head for such a long period.
I had forgotten all these things that I had passed in the master's degree - this was a very good overview of the structural dynamics course for me - thank you Dr. Nafie - it was so good.
It is such a valuable lecture. I don't think someone can explain better than this. Too much appreciated and Very thankful to you sir.
These videos are really helpful, may Almighty God give Dr. a lot of health to continue his work.
Really nice approach and very easy to understand the hidden part of FEM software. Keep it up as you've done so far.
Found a gold. Simplicity at its best. Please do lecture series on non linear time history analysis.
This is one of the best explanations of this topic I've ever heard! You have a real talent for teaching and breaking down complex ideas into understandable pieces.
Thank you very much for the compliments
well done Sir. Very beneficial and straight forward. Thank you for your time
Excellent content and explanation. Thanks for having the rare ability to well-explain this type of topics. Regards from Mexico!
how do you create frame displacement motion in power point
محاضرة مفيش اجمل من كدا ...حضرتك مبتسيبش مجال للاحتمالات في المعلومة او ان الواحد يشك اذا كان فهم صح او غلط بارك الله فيك و نفع بك (حضرتك اسم على مسمى :) )
Excellent. Simplifying the RSA equations into simple term
Dr. Nafie, you are being an incredible help with your videos
I thank you
Gratitude and appreciation from Papua New Guinea 🇵🇬 🙏🏼🤘🏽💯
I am happy the lectures were helpful.
@@drnafie-structuralengineer4620how do you create frame displacement modes in power point
Thank you, corelate your theoretical lecture with practical one using design software this is as a feed back.
Excellent explanation sir . Thank you so much..
Thank you , very match !!! You helped me.... to understand....
Wonderful video, very informative and useful
Thank you what a wonderful and educational video !
I am glad it was helpful.
Just want to drop by and say, "Thank you" for this lecture. This is gold!
Great explanation sir.
The tutorial is so good. Thank you sir.
I am glad the video was helpful
Excellent, simply the best
Thank you very much for the compliment.
Very helpful., Thank you💛👍🙏
Clear explanation. Thank you.
Glad it was helpful
Such a valuable lectures, May Allah bless you🤲🏼
Extermely an eye opening content
Thanks for this excellent video.
Glad it was helpful
THANKYOU SIR FOR SUCH A NICE EXPLANATION
I am glad it was helpful.
Great explaination very clear and easy to understand, keep up the good work sir...🙂
Thank you very much for the compliments
Thank you very much sir
Very good explanation, it will be very helpful if you use an example manual as well as same problem in SAP2000
very informative God bless
Thank you
the explanation is very clear,,thank you for this video.Hoping for another videos related to structural design
I am glad the video was helpful.
Awesome, It's a very explanation I ever met.
I am glad it was helpful
Such a wonderful explanation and still less than 3k views. sad state of knowledge. Please keep up the good work Dr.Nafie.
Thank you. God willing, I will do my best
Marshallah barekallah very nice explained
Thank You
thank you soooo much
more more more please :)
I am glad the lecture was helpful.
God willing, I will do my best to add more lectures.
this video series is very helpful.... please add new videos to it .thanks
I am glad the lecture was helpful.
God willing, I will do my best to add more videos as time permits.
You are wonderful Dr.Nafie...i was worried about how to learn modal analysis...this lecture teach me very good way..thanks...hope to see pushover analysis example made by hand...thanks so much...
Thank you for the compliment and I am glad the video was helpful
@@drnafie-structuralengineer4620 Dr Nafie..you are really wonderfull..i was very depressed about how to learn modal analysis..after searching for long time then getting ypur this beatifull modal analysis video...thanks for sharing..Please if possible can you share this presentation with me by email please...i want it to keep in my document...🙏
Thanks 💜🤗
Really excellent sir , awesome , please sir upload more and more videoa
I am glad the video was helpful.
God willing, I will do my best to add more videos as time permits.
Sir, very good explanation
I am glad it was helpful
this is absolutely amazing please do more on Seismic Analysis
how is that the building can be restricted for only a specific mod shape ?
I am happy the video was helpful
The multi-story building cannot be restricted to only one mode.
But if the building is uniform, the first mode of vibration in which the displacement is increasing gradually with height in one direction will be the dominant mode.
In this case if you used the first mode only in your analysis, and ignored the other modes, your accuracy will be very good.
Thank you, sir. Your video is very helpful, especially for me personally. I hope that in the future you can discuss fatigue analysis (deterministic and spectral) on structures
I am glad the video was helpful.
Unfortunately, I don't have a lot of practical experience in fatigue analysis, so I don't think I will be able to discuss this topic in the near future.
@@drnafie-structuralengineer4620
It’s my first time here, have you already uploaded the lecture about the modal analysis please? If yes can i have the link please? Thank you your videos are very helpful.
Unfortunately, I haven't done a video on modal analysis yet. However, it is surely on my schedule.
Find below the link for my Channel. It doesn't have a lot of videos but I am trying to add as much as I can.
ruclips.net/channel/UC36hwM1et2Psl__WTJuHCHQ
This is pure gold...Clear explanation totally.
Dr Nafie, can you recommend me a book on modal analysis? I am interested in more information about it.
Will you upload a video about center of mass and center of stiffness, and how it is related to modal analysis in seismic actions? (for example if we have torsion of the building in the first mode what shall we do and what is making torsion to happen in the first mode?)
Thank you for your encouraging comments.
You can Try Structural Dynamics by Mario Paz.
I need to add many more videos to cover all the topics of seismic and dynamic analysis.
I ask God to give the time and effort.
Excellent video Dr.Nafie. What an easy way to explain such a complex topic!! Are you planning for any video for Time History Analysis as well? Could you please suggest text/paper for THA of RC buildings?
Thank you for you compliment.
God willing Time history is in my priorities for a video but when I have the time. I hope it can be soon.
@@drnafie-structuralengineer4620please dr.do it hurry i beg you
@@drnafie-structuralengineer4620please explain one research paper thesis as well related to this topic of possible
Nice 👍
Thanks
After a long time research i got the meaning of Response Spectural Curve and it's usage. can you please explain about natural frequency in detail as well?
Dr i appreciate for all your efforts,
I have a question, are the column dimensions are same from floor to floor or it's decrease
Thanks, most clarifying presentation I have seen. Using animation is certainly best method to explain the different modes and their combination. Only thing I didn't catch was the definition of VB(RS), how it was obtained?
I am glad the presentation was helpful.
With respect to VB(RS) it was obtained by taking the SRSS of VB (Base Shear) from the 3 Modes SQRT( VB1^2 + VB2^2 + VB3^2) this gives a value of 986.5 KN. Then this value is multiplied by I/R (1/3) to give a value of VB(RS) of 328.8 KN.
This value is less than 85% of the VB calculated using the Equivalent method of the code (0.85 x 414 = 351.9 KN). So all the Values obtained by the response spectrum are multiplies by a factor of 1.07 So the VB(RS) becomes 351.9 KN
In aggregate, the value of the base shear from the response spectrum is multiplied by (1/3) x 1.07 {986.5 x 1/3 x 1.07) = 351.9 KN
@@drnafie-structuralengineer4620 how to get 414 ?
The 414 KN is obtained using the equivalent method of the ASCE code. This is the basic method used to find the seismic forces. The equivalent method is very simple and is enough for simple structures. For complex structures the response spectrum method should be used.
God willing, I intend to explain this method in an upcoming lecture.
Hi Dr Nafie, how did you obtain the mode shape? I would like to obtain a simple expression for idealizing a building as a prismatic member, I think it can be done, but the hardest trick is the mode shape. And, deflection of the tip of the building I think can also be obtained from the modal participation multiplied by acceleration multiplied by mode shape.
that was a hell of a toturial! thank you so much and hope u can make a video conducting response spercturm analysis using CSI ETABS. one more thing if you don't mind me asking, how can we fulfill ASCE7-10 requirement regarding base shear being 85% more than that of equivalent static method while ASCE doesn's allowe such a method for buildings with some sorts of irregularities.
I am glad the video was helpful.
Regarding the calibration of the response spectrum with the equivalent method, your question is very interesting.
In order to answer your question, I have to differentiate between 2 things. The base shear and the force distribution. The base shear is the total seismic force acting on the building (Sum of all story forces), but how are these forces distributed is the key difference between static and dynamic methods. In the equivalent method, the forces are distributed uniformly from the base increasing in a uniform manner as you go upwards.
In the dynamic method, the forces are distributed according to the mode shapes and may have a completely different distribution if the building is irregular. If the building is regular, the distribution will be very near to the static method.
The distribution of the forces is very important because it has a major effect on the base moment. So you might have 2 cases with equal base shear, but the distribution is totally different so you have completely different base moment which is very important in the design.
Another point to consider, is that the base shear in the response spectrum can not be less than 85% of static ( in ASCE7-10), but if it is higher you don't scale it down.
I hope this answers your question.
@@drnafie-structuralengineer4620 thank u so much, u made so clear 🌹🌹🌹
May I know How to obtain the value (VB)EQ=414 kN in the given example?
Very helpful information. Having these information, shall make me use little time going into books and codes for deeper understanding.
From your experience, which software does these analysis and give good reports?
I am most familiar with ETABS from CSI. Very powerful software but also very expensive. However, I am sure most commercial software will do the Response Spectrum and Modal analysis, like SAP, Robot, STAAD, Midas ... etc.
I am also planning to add more videos about the topic and also include excel files to solve the examples I am including in the videos. However, considering the limited time that I can dedicate to this process, I expect this to be a long term commitment. I ask God to help me.
I am Glad that I was able to encourage you learn more about the topic. Good luck with your endeavor.
@@drnafie-structuralengineer4620 Thanks for your response Sir. I'll surely follow the lectures. Stay blessed
Best visualization of complex concepts in dynamic analysis.. thank you so much sir .
Can I know sir, how and which software you use for these animations..🙏
I am glad that you liked the presentation.
The complex animations is done using Synfig, while the simple ones is done using PowerPoint.
Execellent presentation. I would request to please add modal analysis, because in the absence of modal analysis, series is incomplete.
I am glad the presentation was helpful.
I agree, the series is far from being complete. There are a lot of topics that needs to be addressed and not only the Modal Analysis. God Willing, as time permits I will try to add more presentations.
Eagerly waiting for you upcoming lecture sir..
Hope you upload next lecture as soon as possible..
Your representation is completely conceptual!!
God bless you with his bounties..
Time history analysis also and use softwares as well detail information
Can you please make an example using etabs for fully daynamic analysis procedures
This is a very good suggestion and it is on my list for future videos.
However, my hope to add more and more lectures is not matched by the time available to accomplish these tasks.
God willing, I will try to do my best.
Dr, can you explain this: If I have a square (equal width and length) building and 4 columns each way. That means I have 16 columns total supporting the building. Is the dead load W , the tributary load carried by one column being analyzed and therefore the base shear calculated is that acting on one column? Since each column W is different, then there should be 16 different base shears to do, some likely to be equal.
When we talk about the base shear, we are talking about the total force carried by the whole building. This is to say, the base shear is the sum of the reactions of all 16 Columns
What a great video!
Now i’m carring out a study about “caculating the earthquake by nonlinear method” can you give more infomation about that, please!!! (From VietNam)
I am glad the video was helpful.
If you are doing nonlinear earthquake analysis, most probably you should work with time history analysis.
Are you studying material nonlinearity or geometric non-linearity or both?
@@drnafie-structuralengineer4620 i just study calculate the earthquake for building by Etabs software and understand it's principle
Hello Dr. Nafie. I have a question. How come having a ductile structure is better for non-linear seismic analysis?
A strong earthquake event doesn't happen frequently. Therefore, for economic reasons, we design the building so that in a very strong earthquake it will endure some damage but it will not experience total collapse.
A ductile building can experience large deflection without collapse, but a rigid building will experience collapse at a low deflection level.
We prefer a ductile building, because it will experience a larger deflection and therefore can absorb more seismic energy without collapsing.
Can you make video on temperature gradient analysis in deck superstructure
A Good Suggestion. However, I am currently concentrating on Dynamic Analysis and Seismic Design in which I have more experience. However, I will consider this topic for my future plans.
@@drnafie-structuralengineer4620 your way of explaining concept are really good with a clear video demonstrations.
May I plz know, how did you do that animation of vibration?
It's really great...
It helped a lot in clear understanding
I am glad the video was helpful.
The vibration animation was made using a freeware software called Synfig Studio
@@drnafie-structuralengineer4620 thank you so much for quick reply.
I got the same questions, and the author of this video made very impressive animation, I always want to do the same for my presentations.
If mode 1 has the peak value of acceleration.. Why to consider the other modes? We already have the peak value and we can design for that right?
The final response is a combination of several modal responses. For example if mode 1 constitutes 70% of the response and mode 2 20% and mode3 10%. If you take mode 1 alone you will miss 30% of the response.
However, if Mode 1 constitutes 95% of the response for example then it will be sufficient to take mode 1 alone.
The code requires you to use a number of modes that cover at least 90% of the response. So if mode 1 satisfies this criteria then it is OK to take Mode 1 alone.
Can you please illustrate the regions in response spectrum where is acceleration, velocity or displacement controlled?. I know the regions but I don't understand the reasons
This issue is related to the shape of the response spectrum curve and has no practical importance from a design point of view. There is a region at the start of the curve where the spectral acceleration is constant (the curve is a horizontal line). This is followed by a region were the spectral velocity is constant. Finally in the last region the spectral displacement is constant.
The response spectrum curve in the design codes is drawn as time period vs Spectral acceleration.
If you draw the curve as a relation between the time period and the spectral velocity instead of the spectral acceleration, you will recognize the region were the spectral velocity is constant. The same will happen for the spectral distance.
@@drnafie-structuralengineer4620 Thanks for illustration Sir
Sir How did you find For mode-1 , T1=0.282sec, Mode-2 T2=0.065sec, T3=0.059Sec. Please sir kindly explain.
how to determine the directions of final design story shear force?
Unfortunately, the response spectrum method gives only the design value without sign.
So we take this value and include it in the design combination twice, once with a positive sign and another time with a negative sign.
@@drnafie-structuralengineer4620
you mean one time assumimg every story shear force in positive sign and another time in a negative sign? Could I regard three story shear force always in the same direction?
The direction of the story forces follow the mode shape. For mode shape 1 all the forces were in one direction, so we will take all the forces once to the right and another time to the left.
For higher modes, you will find some stories going right and others going left, the forces will follow the same direction. This is done automatically when you apply the equations as in the example.
For these modes when you put a negative sign for the response, the forces that were going right will reverse to the left and these that were pointing left will reverse to the right.
Excuse me sir, supposed we are going to analyze a structure under a given time history data (ground motion), what would be the difference of using modal time history analysis and direct integration method? I have observed that direct integration takes much more computational power, but at what occasion does it favorable? And let’s say we have obtained enough mode shapes for the modal time history analysis, would the two methods produce same results? Thank you
If you include enough mode shapes, the result will be nearly the same for both methods as long as the analysis is linear. If geometric or material non-linearity is included in the analysis, then you will have to use the direct integration as the modal time history will not be valid.
@@drnafie-structuralengineer4620 thank you so much sir
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........
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May I know How to obtain the value (VB)EQ=414 kN in the given example?