STIFFNESS MODIFIER/CRACKED SECTION ANALYSIS EXPLAINED IN ETABS

[@Decodebd]

The great persons who are disliking my tutorials, I welcome them to comment the reason for their dislike. If there's no reason, only for jealousy you are giving dislike, I will suggest you to ignore my channel & tutorials please. Don't under rate (dislike) any video if you are from a good family.

[@mdshahebaz9567]

U r right sir

[@u_tsf]

yes it's difficult to understand why they dislike without giving the proper reason in comment section .while comment section is open.

[@noahpangpang]

First of all, thank you for all the great videos. They have really helped me a lot. I wanted to clear one thing. In your 10 story building design tutorial, you have provided member beam stiffness modifier of column as 0.7 and beam as 0.35 and 1 as torsional constant. But in frame stiffness modifier ahead, you have provided torsional constant of 0.001 in frame stiffness modifier as well as beam modifier of 0.35 and column of 0.7. However in this video, you have changed torsional constant value to 0.7 in member stiffness modifier. I hope you can clarify my confusion if we need to provide modifer in both frame and member stiffneses or not?

[@Decodebd]

Torsional constant can be provided as 0.001 if beam fails in excessive shear or torsion.

[@EstructuraMX]

@@Decodebd i have seen your video on reducing the torsional constant. But is it safe to do it? because some beams fail and when you reduce torsion the are ok, so yo CAN reduce torsion only on interior girders but not edge beams?

[@jmau065]

@@EstructuraMX It is safe to do it as long as you can guarantee "structural redundancy" of your beams, i.e. you have an edge primary beam that is connected to several secondary beams or the slab itself could take the torsional load. It's all a matter on how you can redistribute torsional demand to flexural demand to other members within the structure. An usual value used for torsional constant is 0.10 to 0.05

[@LWMiraz]

I appreciate the information.

[@Decodebd]

Our pleasure!

[@khalidimtiaz4627]

Very well explained Sir. Thanks a lot.

[@Decodebd]

Welcome.

[@mudherabbas4046]

Very informative...

[@ayazdin8582]

Very well defined with demo

[@sachindeshmukh3228]

Great video👌💐

[@Decodebd]

Thanks for liking

[@dagnadessie751]

that is nice sight pls keep it up, but i have one question if we assume EQ which load combination we prefer for determining section and reinforcement needed for structural members? 10Q for your support!

[@sagurkhan5795]

Assalamoalikum sir... thanks a bunch for shearing new things ... May Allah Grant you Bless

[@Decodebd]

W.Salam. Wc. Ameen. Jajak Allah.

[@CaballeroNocturno29]

Nice and useful video. Theres is a chance than you provide us the presentation?

[@Decodebd]

Thanks

[@Hanns_designs]

For serviceability checks should we use crack or uncracked section?

[@himalnepal9780]

Thank you for the information. So, we should not analyse/design any buildings using the normal stiffness modifiers( all sm=1)?

[@mushasm007]

Could u please elaborate on etabs modeling consideration n design for bi-axial voided RCC slab

[@EzekielMariita]

Hi good and informative video. What app do you use to record the screen?

[@maluandpartners]

bandicam

[@ramiibrahim7488]

great job , go on

[@Decodebd]

Thanks

[@darwisricharlim319]

Thank you sir, keep sharing

[@Decodebd]

Welcome

[@khanthavel6574]

Very useful sir Thank you.

[@Decodebd]

Welcome

[@josschannel4039]

Am using bs code what is the sm factor for beams column and slab

[@KyTaPb]

I have tried to find this kind recommendations for stiffness reduction in Eurocode or Model Code and could find only in chapter that is related to earthquakes. Have You met these requirements/recommandations in other structural codes except ACI? Are these recommendations only for seismically prone areas?

[@fissehamezgebo9016]

JUST LOOK @ 4.3.1 MODELLING PAGE40

[@thanmayivishwanath2591]

Acc to ACI, torsional constant it is considered as 0.35 and 0.7 for beam and column respectively. Why?

[@faribasalimi9397]

Could you please explain why wall stiffness modifier (f11=1.0) while (f22=f12=m11=m22=m12=0.7)?why f11 stiffness modifier is different from others?By the way, I really appreciate the informative video.It helped me a lot to have a better understanding of stiffness modifiers.

[@alexminhnguyen2016]

for wall, or vertical element, local axis 1 is by default, horizontal direction, local axis 2 is vertical direction and local axis 3 is perpendicular to wall face. Open CSI manual you can find the stress direction for each of their element. Here is an example link: wiki.csiamerica.com/display/etabs/Modeling+concrete+cracked+section+properties+for+building+analysis f11 = horizontal in plane stiffness, which will define shear stress (mostly). f22 = vertical in plane stiffness, affect directly to axial stress or wall in plane bending stiffness. f12 = diagonal in plane stiffness. Per ACI or EC cracked wall is 0.35, uncracked wall is 0.7 m11, m22, m12 is out of plan bending or out of plan twisting stiffness, which is not used for shear wall, so we can set these guy back to 0.25, or even as extreme as 0.1.

[@thanmayivishwanath2591]

@@alexminhnguyen2016 Acc to ACI, torsional constant it is considered as 0.35 and 0.7 for beam and column respectively. Whereas others have taken it as 1, why? can you please clarify this

[@thanmayivishwanath2591]

@@alexminhnguyen2016 And Cracked section accoriding to IS 16700 for walls is 0.7, but acc to ACI it is 0.35. Which is correct?

[@waruthp]

Thank you for sharing

[@Decodebd]

Wc

[@S.A.R.Y.]

How to check Global displacement of building at Top level?

[@jijmr2013]

Mr.BD,do you apply the stiffness modifications when you are checking the deflection?

[@jaimeriofrio1174]

@jijmr2013 I have same question with deflection in beams ACI 318-19 cap 24: Table 24.2.2. Maybe, Did you find the answer? Thanks

[@arnelsinconiegue3210]

How would you know or how to determine the member that needs stiffness modifies, how to determine if we need to modify its tension, axial or moment etc.

[@Decodebd]

According to code we need to consider structural members as cracked section, as they will have some cracks under loading after certain period. For considering cracked sections we need to assign stiffness modifiers. If you watch the full video with patience you will know when to use stiffness modifiers for service & ultimate condition.

[@MustafaAhmed-mb7hu]

What will be the moment capacities of cracked members??? Will this be reduced significantly???

[@kal18990]

brother can you attach three etab model mention in tutorial

[@faisaldilshad5373]

Dear Sir, Thank you for this video, just want to ask that torsional constant J is 0.35 for beams but for compatibility torsion can we reduce the value up to 0.001 from 0.35 and if we do that the other values of I (moment of inertia) will remain same for beam i.e. 0.35. Kindly explain. Secondly we provided stiffness modifiers to account for material non linearity which reduced the stiffness. How we will account for geometric nonlinearity which also reduces stiffness. Thanks

thanks for this helpful video. How can you find source of the (f11,f22,f12,m11,m22) on the table minute 10.16

[@Decodebd]

From CSI knowledge article.

[@gowthamsiva3611]

how to apply modifiers in walls, in memberane or bending?

[@mohammadismail3970]

Thank you Bhai

[@Decodebd]

Wc

[@vasubhadania]

How can we use this aspect in Tekla

[@DINESHMaharjan-pe8mt]

What says in IS 456 code about stiffness modifications?

[@challengemyselffrom100toab2]

Can i get that slide?

[@maluandpartners]

Can you start replying to other comments in the video? I can see in all your videos you reply only to comments which says good video or informative video.

[@ahasanahmed7099]

Thanks a lot bhai...

[@Decodebd]

Wc.

[@nhandoan7863]

Dear sir, I saw you reduce the F22 for Wall. In guidline of CSI F22 corresponding to EA (axial stiffness) so i think arrord to ACI318, Axial stiffness no need to modify Am i wrong? can you explain to me with more detail? Thank you so much.

[@faribasalimi9397]

Hi,I am wondering why in the video the slab stiffness were not modified.Thanks in advance for the response.

[@Decodebd]

This is just comparison for beams & columns. Check recent course in building design we changed stiffness for slab also.

[@civilEngineering1145]

Should we do reducing the stiffness for seismic analysis?

[@Decodebd]

Yes for 2 different purpose 2 different chart (Service Condition, Ultimate Condition).

[@civilEngineering1145]

@@Decodebd thanks dear,i mean to do the stiffness for the both seismic and non seismic condition should?

[@bijoychondojony8800]

thanks man

[@Decodebd]

Wc

[@mdshahebaz9567]

And sir what about indian code.

[@veerappan1000]

Thanks a lot

[@Decodebd]

Wc

[@langparisse9185]

Where can I find this table?

[@langparisse9185]

Chart for using stiffness modifier in structural analysis & design

[@harfianashari2704]

can you add english subtitle for this video

[@Decodebd]

The video is already in English

[@harfianashari2704]

@@Decodebd but for someone who arent good at listening english language it become a problem. So if you have time please make the subtitle ☺️

[@pavelukraine4929]

@@harfianashari2704 There is written exactly the same what he said

[@mdtariqulislam2795]

thanks

[@asim3n3]

Thanks for this informative video, but I have a concern regarding deflection and drift check as per UBC it is mentioned as following: UBC 1997 1630.1.2 Modeling requirements: The mathematical model of the physical structure shall include all elements of the lateral force-resisting system. The model shall also include the stiffness and strength of elements, which are significant to the distribution of forces, and shall represent the spatial distribution of the mass and stiffness of the structure. In addition, the model shall comply with the following: 1. Stiffness properties of reinforced concrete and masonry elements shall consider the effects of cracked sections.

[@Decodebd]

What is the concern?

[@asim3n3]

@@Decodebd concern is if the code say that members need to be cracked then how can to we check the deflection using without modifying stiffness.

[@Decodebd]

Check the tutorials carefully. We have stiffness modifier(1.43 times of Stiffness modifier for Ultimate condition) to consider cracked sections for serviceability checks.

[@asim3n3]

@@Decodebd thank you.

[@Decodebd]

Wc