Session 24 - Stiffness modifiers as per IS codes - Bhavin Shah

#stiffnessmodifier #earthquakeresistantdesign #structuralengineering
Link : sqveconsultant...
The concept of stiffness modifiers was introduced for the first time 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. Thereafter, stiffness modifiers were defined in IS 16700 as well. In IS 16700, stiffness modifiers are specified for serviceability and ultimate conditions. There are certain practical difficulties as it is a relatively new concept for the Indian Standards. Few questions are as follows:
1. How in one model we can take for strength criteria with stiffness modifier and for serviceability without modifier?
2. Why stiffness modifiers are used for earthquake only ?
3. Reason why and when to use these modifiers...
4. Do stiffness modifiers reduce the earthquake load taken by the members?
5. Difference in modifiers for service and ultimate condition...
And many more...
We will discuss such interesting points in the next live technical discussion.
DATE : 25-SEP-21
TIME : 7:00 PM
Speaker : Bhavin Shah, Founder & CEO - SQVe Consultants
You would be able to interact with us in the session through LIVE chat. Please click on "Reminder" button to receive the notification when we go live.
May please share the message with the interested engineers in your circle.

[@gtuallupdates2320]

Sir I have some queries like
1. As I'm using etabs for modelling you had said in etabs first we have to analyse for gravity loads and then for seismic forces so my question is for first time do we have to analyse for only gravity load with no eqx or RSx and for second after applying modifiers we have run for only seismic forces or run for all the load cases please explain.

[@vasubhadania]

what about walls when used as retaining wall....(we cant always ignore them as they might also be on ground level)...??

[@StructuralEngineering]

Yes, stiffness modifiers for the same may be considered as per IS 16700.

[@vasubhadania]

@@StructuralEngineering so according to table 5 in IS 16700 for strength stiffness will be 0.7 for retaining wall too....?!

[@shravanpoddatur912]

after applying modifiers, the deflection and displacement will not satisfy w r t before applying modifiers. is it require to increase sections.

[@StructuralEngineering]

yes, it is required to increase the sections in such case.

[@Zorot99]

Sir is there a need to use stiffness modifiers when the building is not under seismic or wind load?

[@StructuralEngineering]

Which is the type of structure? At least, stiffness modifers for serviceability case to be used if seismic load is not present.

[@Zorot99]

@@StructuralEngineering usually residential buildings that are less than 5 storey, as I mentioned no wind or earthquake.

[@StructuralEngineering]

@@Zorot99 There is no demarcation in our IS code that stiffness modifiers could be excluded for smaller buildings.

[@Zorot99]

@@StructuralEngineering what about the absence of wind load and earthquake?

[@civilideas1925]

👍🏻

[@StructuralEngineering]

Thanks

[@Yty_4455]

14:20. , 59:00