Static Seismic with IS1893 - pt.6: Structure Type (ST) & Time Period || Bare MRF building, RC walls

In this video, I will discuss about ST parameter in STAAD, how time period of different structure is calculated following the guidelines of cl.7.6.2 and its impact on seismic analysis. Time period and structural behavior of a building with and without infill wall is different, how we can consider this additional stiffness of wall during seismic analysis, that I will cover in detail.
For analysis and design of any structure (concrete, steel or composite) which is in low or high seismic prone area, we need to perform a detailed seismic analysis and based on the analysis results, go for member/connection design. Static seismic analysis is one of the easiest method of earthquake force consideration but it is not only limited to that. For dynamic analysis and seismic detailing, we need static seismic inputs.
Previous Part--
Part 5: Basic Seismic Definition || Z,I,RF, DM, SS || Auto-Generate value -- • Static Seismic with IS...
Next Part --
Part 7: Time period for Walls (ST 4,5) || RC, URM Infill Wall || cl.7.6.2 -- • Static Seismic with IS...
For more details on Seismic analysis, check this video --
• Modelling for Seismic ...
Also check this playlist --
• Seismic Analysis with ...
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[@fazalarju]

Sir,
in your first modal though wall is not modelled we assign wall load as member load and practically there is infill wall. we should consider "all other bldg" i.e time period T=0.09h/sqrt(d) instead of 0.075h^0.75 as u demonstrated. pl confirm and clear it sir

[@surojit_ghosh]

Under cl.7.6.2, code suggests to use eqn.1 for buildings without any masonry infill and eqn.5 for buildings with infill walls. Also under cl.7.9, the process to model this URM infill wall for seismic analysis is provided. Now, if you want to consider eqn.1 without modelling the URM infills (which contribute for lateral load resistance by forming load path) just by assuming it is there, then it is up to you. But structurally the models (with and without modelling walls) are not same, you can compare the time period of these structures by extracting the natural frequency.

[@Enfld1122]

If the infill walls are present in architecture drawing, but in staad pro , diagonal struts are not modelled, then which formula should be used for estimating time period? As per IS 1893 part 1) , (a), (b) or (c) ??

[@surojit_ghosh]

It's either 2nd or 3rd equation under (a), depending on the type of wall. For RC concrete wall, it is 2nd. For brick wall, it is 3rd.

[@Enfld1122]

​@@surojit_ghosh if the structure consist of both RC walls and brick walls, then which equation should be used?

[@Enfld1122]

If the structure consist of both RC walls and brick walls then which time period formula should be used??

[@surojit_ghosh]

As RC wall provide more lateral stiffness, you need to consider the equation corresponding to that.

[@nooranistores8015]

Sir, kindly upload this week video (part 7 of seismic analysis..)

[@lutforrahman929]

please upload video on bracing system, location of bracing and load path

[@VipinKumar-du3oq]

Sir Kindly make video on Wind Load
I'm so confused after seeing different videos on youtube, they all are teaching differen

[@nooranistores8015]

Sir, as you say that more stiff structure has lesser time period and thus it attracts more seismic force, ok.. But my question is we aren't model floor slab in model and applying slab load to supported beam, but practictically, there is a slab present, and due to slab, more seismic force is attracted, but we aren't model slab in our slab model, so there would be lesser seismic force computed by staad, which is mismatching, sir kindly explain on that...
2- sir,will there any contribution of modelling rigid/semi rigid diaphragm on time period? please reply, thanks.....

[@surojit_ghosh]

It is not a correct technique to ignore the floor slab during modelling. A floor slab normally behaves like a rigid diaphragm and it is always recommended to define the in-plane rigidity using FLOOR DIAPHRAGM command In STAAD, and for flexible diaphragm, using plate mesh. Not modelling the slab as a rigid diaphragm not only changes the structural behavior, also several checks (eccentricity checks, torsion) are not performed if it is not present in the model.

[@nooranistores8015]

@@surojit_ghosh sir, can we model slab along with rigid floor diaphragm simultaneously??

[@surojit_ghosh]

FEM slab behaves like a flexible diaphragm whereas FLOOR DIAPHRAGM behaves like a rigid diaphragm. Hence both is not required/suggested.

[@nooranistores8015]

@@surojit_ghosh but if we haven't model slab, it attracts lesser seismic force than actual,as time period cycle is less, and if we model slab,the floor rigid diaphragm and slab nor recommended simultaneously, both side we have drawback, what's the straight forward solution for it?? Or it is the lacking of staad pro??

[@VipinKumar-du3oq]

How do i contact you sir as i want to learn more some specific topic regarding structural designing. I also tried to contact you on linkedin but here it shows to message you i have to go premium

[@mateenahmed7243]

How to see graphy in staad pro

[@surojit_ghosh]

Your question is not clear to me. Do you want to check graphs? which one?

[@nooranistores8015]

1-Sir, staad pro itself calculates time period, then why we need to manually input time period??
2- Do we model URM infill wall in staad every time when walls are present in our building or we ignore it to model and effect of URM taken in model??