Modelling for Seismic Analysis in STAAD || ASCE 7-16 || IS 1893(Part 1) || Acc. Torsion & Diaphragm
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- เผยแพร่เมื่อ 22 ก.ย. 2021
- Consideration of seismic analysis and effect of seismic force on various structural components is required for all types of building structures. If a structure is not modeled properly to withstand seismic forces, then it might be unsafe.
In this video, I will discuss about the basics of static seismic analysis and modelling of structures for seismic analysis. I will cover different international codes which are available for static seismic analysis in STAAD, a brief discussion on the newly implemented IBC 2018 code, different options and parameters required for static seismic analysis. Then I will cover the mass and stiffness modelling, how to define the seismic mass more effectively both for static and dynamic analysis, different types of diaphragms and their effects on seismic behavior and finally how to model the diaphragms and shear walls easily using the advanced options available in STAAD.Pro CONNECT Edition. Also we will discuss about accidental and inherent torsion and how to consider it for seismic analysis.
Chapters--
0:01 Introduction
1:06 Basic of Seismic Analysis
2:52 Seismic Analysis Methods
7:48 Static Seismic Load
14:30 Mass Modeling for Seismic Analysis
30:56 Apply Seismic Load on Structure
32:30 Floor Diaphragm and Torsion
49:42 Vertical Irregularity
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thanks a lot for making these enriched & genuine videos on staad pro-keep it up
thanks for these enriched videos-keep it up-excellent work
This is helpful for the beginners/intermediate learners of staad pro like me. Thank you very much.
Thanks, next part of this series is now published on Mass model generation for static and dynamic seismic analysis. You can check it from here - th-cam.com/video/6QXkNcAN_8E/w-d-xo.html
Excellent presentation !!
really helpful video. Thanks alot for sharing.
Best explanation video i have found on internet. Thanks a lot . Can you please make a separate video showing different types of irregularities as per is 1893 :2016 of a particular model & how to handle them.
Thanks in advance for your effort.
Surojit, Please make a video on Plate Elements, How to keep the axes system, What is Mx, My, Sx, Sy, Global Moments etc,............
Very very informative vedio sir
Best sir
If there is a cut out in slab how rigid diaphragm is given not understood. Pl tell me in detail.
Excellent. Can upload the STAAD file for all the lectures as reference and to analyse your skills?
Surojit,
Excellent videos. Update and/or delete the old videos to reflect latest version of V22 update 8.175 version, so users don't get frustrated.
In reference mass load type, dead & live load in gravity direction (-ve sign) is copied/used to calculate static seismic weight.(timeline 25 min onward). For dynamic same is repeated for all three directions viz x,y & z with -ve sign in reference mass load type. Aforementioned 25 min onward to eliminate tedious task of considering same in seismic definition & in dynamic load case. My question,1. does staad calculate seismic weight for static & dynamic if we define dynamic mass in reference i.e in all 3 direction?. 2. Does -ve sign in reference mass is same as +ve sign as long as the direction are same in all 3 direction?.
1. Yes, STAAD internally calculates the seismic weight for static and mass model for dynamic analysis directly from a mass reference load case with mass defined in all 3 directions, this is discussed in detail in this video -- th-cam.com/video/6QXkNcAN_8E/w-d-xo.html.
2. Mass is sign less, so theoretically we need to specify it as a positive number. But if it is copied from a primary load case to a mass reference load with negative sign, then during seismic mass/weight calculation, program converts it to positive mass. Just create two instance of the same model with + and - mass, you will notice same seismic weight/mass is considered for static and dynamic analysis.
Good explanation. I need to know that Floor Diaphragm option shall be applied only for Concrete Slab integrated with Steel structures or it can be used for Concrete Structures also? Also if I consider Concrete slab as Diaphragm which can resist lateral forces, Can I eliminate Plan braces(in steel building) in that level ?
Using Floor Diaphragm, we can consider the in-plane rigidity of a slab, whether it is a RCC, PT or composite deck. It is one of the easiest way to consider the in-plane stiffness and torsional effects during earthquake analysis without modelling the slab with FEM.
Yes, you can use this for concrete slab (assuming it is a rigid type diaphragm). If you specify a floor diaphragm at slab level, you can eliminate modelling the plan braces, but for accurate analysis, it is always better to model the correct structural components.
@@surojit_ghosh Thank you for the reply. Can you please share the marco file for Auto-generation of Gravity Loads under Reference Load definition ?
good one. please make a video how to apply wind load as per IS 875 on the Truss roof in STAAD Pro
Thanks Abhijit, yes I have some plan to post few videos related to wind load application on different type of structures.
Hi Great work. While designing multi storied building I have seen columns in the top level has more moment compared with bottom level. Can you help how to solve. Particularly in the case of gravity loads. Thanks.
For any high rise building, peripheral columns are subjected to more forces/moments at higher elevation due to the lateral forces, this is normal. Can you check and confirm that the higher moment is due to the gravity load, not for a lateral load or combination case?
@@surojit_ghosh Thanks for your reply. The higher moment is due to gravity load. Can you please share your mail ID. I will mail the staad file.
How to find that dynamic seismic 100% of static seismic?
Greetings, where i can get the macro you are using to generate Mass Refrence Load ....thanks.
This is one of my unpublished macro that I created long time ago. Using this macro, I can skip the entire mass model generation process and for a large building structure, it saves lot of time - I normally define the gravity loads under primary load cases and use this code to generate mass modeling.
@@surojit_ghosh Yes it is very good tool , I hope I could get it
Auto-generation of mass model is now included in the latest version of STAAD.Pro CONNECT Edition (Update 9) as a default feature. You can check this video for more details -- th-cam.com/video/jPUOGACnIM4/w-d-xo.html
Thank you so much 🌹
A particular use case example for static analysis only, demonstrating the theory would have been very useful. A lot of information has been given in the video but it becomes confusing since dynamic analysis and static analysis all seem to be combined in the same model and this video is supposedly about demonstrating static analysis. The final effect is that it's somewhat confusing to beginners to apply the theory to a particular model.
This is not actually a demonstration of static seismic analysis, rather this is one of my webinar on seismic analysis that I delivered early this year. Few modeling techniques are common for static and dynamic analysis like modeling the diaphragm, consideration of seismic mass and accidental torsion. So I have used dynamic analysis as a reference to elaborate how the modeling approach will help if response spectra load is added to the model. I admit that all these information might be confusing for any beginner.
I will start a separate series on seismic analysis later this year covering all aspects and I am sure that will help you to understand the details.
Thank you for clarifying the matter, it would be really helpful for beginners when you publish your series.
Nice presentation,may i have this macro for generating mass model?
And may you please upload a detailed explanation of wind load as you did for seismicin this video.
Separate macro is no longer required to generate mass model. Since STAAD CONNECT Edition Update 9, an option is provided which can be used to generate mass model. Check this video for more details -- th-cam.com/video/jPUOGACnIM4/w-d-xo.html
Sir how to take account vertical earthquake effect as per 1893:2016
You need to apply vertical earthquake loads under a separate load case following cl.6.4.6. of IS1893(part 1):2016. I will discuss this topic in detail in this series -- th-cam.com/play/PLxLi_mmlPeioCvBiFgvejNGzC14ocb87i.html
Thank you very much sir .Waiting for video upload .
Sir please share your staad file...thanks
Excellent. Can I have the lecture pdf I want to keep is as reference?
Thanks Hazim, at this moment I don't have the pdf copy of this presentation, actually I have never thought about it. I will try to generate the pdf copy and upload the link in the video description.
@@surojit_ghosh Nice and it will be great reference for future.
@@surojit_ghosh hi still waiting if possible to post the pdf and model. That will be great.
Can you add the model in the description? It will be great to experience and play with this model. Thanks
Sir can you make modeling course for beginner ?
At this moment, I don't have any plan, but I will obviously consider this in future.
Great job ...Could you please upload the lecture pdf to keep it as a reference. thanks in advance
Thanks Ebrahim. Yes, I will upload the transcript soon, it is not ready yet.
@@surojit_ghosh thank you very much 🌹
Sir,
What is basic difference between static & Dynamic analysis?
If you want to consider the actual behavior of a structure subjected to earthquake load, you need to perform proper dynamic analysis. Equivalent Static method of seismic analysis is an approximate method, it assumes that fundamental mode of vibration is predominant, neglecting all other modes of vibration. As per IS 1893, it is applicable for regular buildings located in seismic zone II with height less than 15m. Whereas when you perform response spectra analysis, it considers the structural response of each mode and finally use any modal combination method to find peak response.
There are several differences between these two approaches and you can go through any standard textbook to know more about dynamic analysis.
@surojit Could you please explain how to define the floor diaphragm in order to let only shear/core walls resisting the lateral forces and other elements (in my case steel structures) only transferring those forces to the shear/core? Could you share your email ID? Thanks in advance.
When a lateral load is applied on a structure, that load is transferred to the support using a proper load path. For lateral load, this load path consists of members/elements which are specified as lateral load resisting element like shear wall, bracing etc. If you don't define any member specifically as a lateral load resisting member, then all connecting member to the slab will be subjected to force depending on location and stiffness. If you can define the dual framing system (Gravity+Lateral separately), then it is possible.
In STAAD, there is no option available to define dual framing system (like RAM Structural System) but you can manually define this using release command and using CHANGE command to separate lateral load from gravity load cases.
@@surojit_ghosh sir can you please spread some light on how to use those commands
Sorry, I am unable to understand your query properly. Which commands are you looking for?
Dear sir, can you please share your email id plz!