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How to model Connectivity between Raft Footing and Wall in Staad?

 
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Muhammad_Hasan
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Joined: 27 Feb 2017
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PostPosted: Sun Sep 09, 2018 1:15 pm    Post subject: How to model Connectivity between Raft Footing and Wall in Staad? Reply with quote

Good Everybody,

I am Modeling a Circular Digester tank of 318Million Litters per Day , I have a doubt how to model the connection between the wall and raft footing.

this how I modeled the Raft is 600mm thk and the wall is 350mm thk, I have modeled the walls directly from the raft plate nodes with first layer of the wall to height of 300mm which will be part of raft too how to model this this part of the wall that is inside the raft which type of plate release should i use to simulate the actual behavior.
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ibu_4_u
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Joined: 14 Sep 2009
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PostPosted: Mon Sep 10, 2018 1:37 am    Post subject: Reply with quote

Dear Muhammad_Hasan


Rearrange the plate sizes of wall as per thickness of raft, and avoid the stresses of plate coming in the Raft Portion,

In staad corner Stress option is are also there, if you want to check stresses or moment at specific location in plate.

However as per my suggestion, don't prepare the bottom raft with plate connected to wall, instead do wall designing seperetly with considering fixed support condition and footing with retaining wall criteria "heel & Toe".

Thanks & Regards
Ibrahim Vepari.
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podianu1
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Joined: 23 Mar 2013
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PostPosted: Wed Dec 12, 2018 8:50 am    Post subject: Reply with quote

Hi;
1. I presume that the model you have created is to find out the various stresses specifically hoop stress for which the steel needs to be provided. Being circular IS 3370 Pt IV offers coefficients that help you compute the forces and arrive at the quantity of steel and thickness of walls. There is also the matter of the design philosophy adopted whetheer WSM or LSM. Generally WSM has been adopted extensively for design of liquid retaining structures. You could adopt LSM as well but crack width calculations will be required to be done. All these are manual calculations, STAAD models and design modules dont offer insight into these. Hence doing the wll and the conical dome separately may be ideal and preferably manually.

2. Regarding the design of rafts you could mode;l it as a raft on soil springs with the wall loads transferred along the circumference of the wall, I daresay this may not be as critical as we think, weight of water and uplift pressure in case of tank empty condition may be more critical.

3. Hope this gives you some inputs.
Regards
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