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connection of columns at plinth level and floor level with beams

 
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jagan0819
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Joined: 30 Mar 2016
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PostPosted: Wed Feb 26, 2020 10:28 am    Post subject: connection of columns at plinth level and floor level with beams Reply with quote

hi sefians

i have a doubt in modelling of a structure(G+1) in staad ,i.e should all the columns at plinth level and floor level(in both directions) get connected with beams. if yes is there any specific reason behind that and if no is there any parameter in staad that we should provide.

image was attached( PLS OBSERVE C14,C15,C16 )

regards



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sukanta.adhikari
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Joined: 26 Jan 2003
Posts: 727

PostPosted: Thu Feb 27, 2020 4:32 am    Post subject: Re: connection of columns at plinth level and floor level with beams Reply with quote

It is a good practice to connect the all the columns together.As per older version of IS 1893(You can check the new one)

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7.12.4 Connections Between PartsAll parts of the building, except between the separationsections, shall be tied together to act as integratedsingle unit. All connections between different parts,such as beams to columns and columns to theirfootings, should be made capable of transmittinga force, in all possible directions, of magnitude( Qi/wi) times but not less t&m 0.05 times the weightof the smaller part or the total of dead and imposedload reaction. Frictional resistance shall not be reliedupon for fulfilling these requirements.
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If there is no restriction connect all the columns.But practically it is not possible always...sometimes in Industrial building/structure we are not able to connect columns in all direction.The layout is such that  pipe trench,cable trench,equipment foundation comes in between..and we can't convince the technical person of other discipline nor the client to change equipment disposition/trench etc..So in that case you can use ELX and ELy parameter in staad.

Here is the link to use it

https://www.sefindia.org/forum/viewtopic.php?t=14625

In your case it seems that there is no restriction,so it is better you provide it ..Since the columns are tied in the direction of major axis and not in minor axis.


Regards
S adhikari





jagan0819 wrote:
hi sefians

i have a doubt in modelling of a structure(G+1) in staad ,i.e should all the columns at plinth level and floor level(in both directions) get connected with beams. if yes is there any specific reason behind that and if no is there any parameter in staad that we should provide.

image was attached( PLS OBSERVE C14,C15,C16 )

regards
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syed_A
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Joined: 22 Oct 2011
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PostPosted: Thu Feb 27, 2020 5:27 am    Post subject: Reply with quote

Engr S adhikari
Since the plinth beam rest on ground, Do we need to consider  support conditions in staadpro or simply model it as any other beam which supports slab, wall etc
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atul_123
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Joined: 29 May 2009
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PostPosted: Mon Jan 20, 2025 6:29 am    Post subject: Reply with quote

Plinth beams in a building has primarily 2 functions<o></o>
1) To tie the columns <o></o>
2) To support the walls at ground floor level <o></o>
Your question is pertaining to point When the beam issupported on ground, you can have 2 situations,
a) The soil is hard.<o></o>
b) soil is soft.
In Case (a) when the soil is hard, then the soil has the ability to hold theload that is coming from the wall. It is continuously supported on the groundfor gravity case, and hence the beam may not bend at all. The load directlytransfers to the soil without creating any force in the beam provided you havewell compacted the earth.
However note that in many cases, site does mass excavation and refill afterfoundation is constructed and all this decides if the soil is well compacted.
Please note that plinth beam is also a part of the frame and hence it will beresisting lateral forces and hence the size and steel in the beam won’t beconsiderably less/nominal.

In case (b) when soil is soft, then even for gravity case the beam may bepartly or fully subjected to bending.
It is difficult to capture the bearing on the soil and you may want to go witha conservative approach.
Note that ETABS also has an option to use a line spring for beams. However, Ibelieve it is not worth spending time doing all this instead look at the designwholistically and see if any reduction in wall load really changes anything asseismic point of view the steel is any way not going to be too less. Only itreduces some mass of the wall in the design.
<o></o>
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