Session 2 - Stiffness modifiers as per IS 1893 (Part 1) : 2016 - Live Technical Discussion

SQVe Consultants have taken up the initiative for launching the "weekly live technical discussion" series for focusing on the areas wherein industry is facing practical difficulties. To know more about SQVe : sqveconsultants.com
The topic will be decided in advance and the technical discussion will be conducted through the live stream at youtube. The sessions will be organized on every Sunday at 11:00am.
Facilitator : Bhavin Shah (Founder & CEO, SQVe Consultants)
We have received request from few engineers for taking up the discussion on stiffness modifiers in Weekly Live Technical Discussion.
The concept of stiffness modifiers is introduced in IS 1893 (Part 1) : 2016. The clause no. 6.4.3.1 of the code defines requirements for structural analysis. It is mentioned in the clause that for structural analysis, we should consider reduced moment of inertial for RCC structures. For columns, 70 percent of Igross should be considered and for beams, 35 percent of Igross to be considered. This clause has generated many questions among the group of structural engineers.
Bhavin Shah created a brief note on stiffness modifiers based on the questions received from the engineers. The same can be accessed at : sqveconsultants.com/2020/09/1...
In the upcoming session of Sunday (20-Sep-20), we will focus our discussion on the stiffness modifiers as per IS 1893 (Part 1):2016. Stiffness modifiers as per IS 16700 will be taken up in the session of (27-Sep-20).

[@samviladnan7866]

And here is something which is more valuable than gold Thank you sir Eagerly waiting to join for coming discussions

[@StructuralEngineering]

We are glad that you have liked the session. Looking forward to meet you online in the upcoming discussions.

[@gowthamsiva3611]

sir, these good information

[@StructuralEngineering]

Thanks for the message.

[@ramataipawar9434]

Very informative session, thank you sir actually I am searching the research in use of biomass in civil engineering material

[@StructuralEngineering]

Use of biomass in civil engineering is indeed a good topic. So, what are your overall aims for the research?

[@justinejoseph9925]

Sir, How can we apply stiffness modifiers only for seismic load cases. Because as per my idea, we apply SM to the particular section and after various load combinations are made( be it seismic and other combinations.) and analyse. How can we negate combinations other than seismic while doing analysis ? Kindly explain

[@StructuralEngineering]

At present in STAAD, stiffness modifiers are applied only to seismic loads. In ETABS, the stiffness modifiers will be applied to all the load cases. For more details, you may connect with us through email address: [e-mail]

[@user-xh8hd2nc4b]

Is there any upper bound time period limit after applying SMF.
Like i have a building of 48m high above ground. At what amount of time i should restrict my analysis.

[@StructuralEngineering]

Your query is related to maximum value of time period which allowed by the code, right?

[@user-xh8hd2nc4b]

@@StructuralEngineering yes. For better performance of the building.
when we use the SMF time period will increase.
For my case after using SMF T increased from 1.9sec to 2.8sec.
For 2.8s if the structure suffices the SLS condition. Am I okay to go for designing or should i work to reduce T?

[@chiragjain8027]

1.Push-over analysis Guidelines for retrofitting.
2.Extended End plate Connection.

[@StructuralEngineering]

Good suggestions Chirag for future topics!

[@bnks5693]

Sir, in my analysis i found out that less % of steel is required in building with Stiffness Modifiers in comparison with building without SM

[@StructuralEngineering]

Interesting! Can you please share more details like height of building, type of building, impact on time period, % reduction in steel, etc. ?

[@sarojtamang2]

I have experienced the same, dont know the reason behind it though.

[@StructuralEngineering]

Your further views/comments are welcome on the subject.

[@balakrishna4148]

Next week are we going to discuss stiffness modifiers as per UBC-97

[@gowthamsiva3611]

where shall we apply modifiers for shearwall, memberane or bending=0.7

[@StructuralEngineering]

Pl refer this video for details : ua-cam.com/video/TimdYjeVGDo/v-deo.html

[@bnks5693]

Sir, do we need to apply SM in equivalent static Method...Thank You

[@StructuralEngineering]

Good question! Let's connect over a call to understand it in more detail.

[@rishabh6155]

Sir, but in a telegram group of ETABS, Dr. H.J Shah sir has told that SM should also be used for the gravity loadings. But you said that it should only be considered for seismic loadings.

[@StructuralEngineering]

Thanks for raising the question! The entire discussion in this video is related to stiffness modifiers as per IS 1893 (Part 1) : 2016. As per the IS code, the modifiers are specified only for the seismic load. I hope it clarifies your doubt.

[@rishabh6155]

@@StructuralEngineering Sir but the cracks will also generate in the case of only gravity loads. So why it is not necessary to use modifiers in that case?

[@StructuralEngineering]

@@rishabh6155 Let's connect separately to discuss it in more details.

[@rishabh6155]

@@StructuralEngineering okay sir, but how and where?

[@StructuralEngineering]

@@rishabh6155 Please drop an email to [e-mail]

[@shefalithakkar7929]

I have a question that how much it will be real that we decrease stiffness equally for all beams and columns and then attract less earthquake..In actual scenarios earthquake will be applied to the elements which may have more stiffness then the reduced stiffness due to these modifiers..I do not find actual relevance of these clause,as by using these clause we will design our elements with lesser earthquake forces than actual..please clarify my understanding sir.

[@StructuralEngineering]

It is very important question. Let's talk over phone at convinient time.

[@VijayKumar-ew8gl]

Sir how do modifiers affect support reactions??

[@StructuralEngineering]

Stiffness modifiers would result in the redistribution of forces due to change in stiffness. Further doubts/queries are welcome.

[@arijitdey13]

Why SM with P-delta will increase force in column as drift will be more...I didn't get...can please explain? (57:20 by Harish Patel)

[@StructuralEngineering]

With stiffness modifier the structure will be more flexible. At the similar time, P-Delta analysis would result in the higher drift due to geometrical nonlinearity. Hence, combination of both P-delta and SM would increase the drift and in turn the forces in the members would increase accordingly. I hope it is clear. Please feel free to share if there are any further doubts.

[@ashfaksk9316]

@@StructuralEngineering how much percentage of dead load we should consider if we consider p-delta analysis & why

[@StructuralEngineering]

@@ashfaksk9316 100% of dead load to be considered for P-Delta analysis. Along with dead load, live load also needs to be considered. We may discuss it further, if required. Please connect with us through email : [e-mail]

[@krititiwari2235]

Are stiffness modifiers required only for analysis or for design as well? Please clear the concepts

[@StructuralEngineering]

They are required only for analysis. The forces derived from the analysis will be used for the design. For the design, concept of limit state design of method will be used. For further doubts, pl feel free to contact us at : [e-mail]