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In structure static analysis gravity of structure generally considered or Not

Question asked by Shiva Kumar Bairoju on May 15, 2014
Latest reply on Apr 18, 2016 by Kapil Kumar

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In structure static analysis gravity of structure generally considered or Not ?

If we won't give gravity to the structure,structure self load may acct on the body or Not?

How the structure self load acct on the body.....It depand's on gravity or any other condination

Exp...

Right nw i am doing container structure static ansys..

Cantainer structure weight apprx 500kg

External load's accting on structure apprx 400kg

Cantainer bottom fixed.

In this case....Gravity may apply or not.

How the cantainer self load may acct on body.

I got a little confused about it.what is your view on this.

No one else has this question

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Shaun Densberger May 15, 2014 1:50 PM
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If gravity is present in the physical system, then you should include it. The finer point is whether or not you consider the changes in the structure's stiffness due to the self-loading stresses.
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- Shiva Kumar Bairoju @ Shaun Densberger on May 15, 2014 2:33 PM
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  Sorry to say this......
  i didn't get u actually wat ur saying....
  
  When we are doing any static structure ansys,do u applying gravity for that.
  otherwise just applying external load on structure.
  do u tell me any particular case...for example......... gravity effect'sv in static ansys
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  - Shaun Densberger @ Shiva Kumar Bairoju on May 15, 2014 3:21 PM
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    When we are doing any static structure ansys,do u applying gravity for that.
    
    First things first, I assume that by, "ansys" you mean analysis, and no the multi-physics software package ANSYS.
    
    Anyway's, if the physical, real-world system that you are modeling with your finite element model is under the effects of gravity, then yes, you should include it in your model. That being said, the effects of gravity may or may not have a discernable effect on the results; this depends on the characteristics of the system.
    
    As I said earlier, the finer (and more important) point is whether you need to consider the changes in the system's stiffness due to gravity. In the real-world, you container is in a state of stress due to gravity prior to it being loaded with other objects; this stress state can modify the container's stiffness characteristics. Whether this pre-stress increases or decreases the stiffness characteristics of the container depends on the conditions of the system.
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    - Shiva Kumar Bairoju @ Shaun Densberger on May 19, 2014 11:53 AM
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      Thks Shaun Densberger.........
      
      Sorry....(When we are doing any static structure ansys,do u applying gravity for that) Analysis Only..
      my intention is actually right nw i am doing Design & Validation both...
      Design in Solidworks And at the same time validation also in Solidworks Simulation only.....
      i am confuced by this gravitational effects on any body&structure any thing......
      gravitational forces may effecty on that part&body&structure.........Every one know that in Earth 9.81g.
      But how this Gravity effects on that body.......evey action there is an rection in this theory if we applying extranal forces on static analysis what is the roule of Gravity in this Static Analysis......
      
      if the physical, real-world system that you are modeling with your finite element model is under the effects of gravity, then yes............ya of course in real-world any system under the effect of gravitty only.....So we consider gravity for all those system's...
      
      Any way i got ur point....If passble give me ur Mail-ID i will catch u there..
      
      Thkss.....
      
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Kumar Dandapani May 16, 2014 6:01 AM
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Hi Siva,

1. In your case if your considering effect on self weight then you must consider the self weight (in loads add gravity) otherwise. Container self weight not included in FEA. so that your getting displacement and stress must be a minimum what your getting actually.

2.In case if your not considering self weight of the container then you can proceed without defining the gravity in loads.In this you will be getting the displacement and stress with external load only. Thanks

A.D.Kumar,
EGS Computers India Pvt Ltd
http://www.egsindia.com
http://www.egs.co.in
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- Shiva Kumar Bairoju @ Kumar Dandapani on May 23, 2014 10:08 AM
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  Hi Dandapani...
  
  That what i am asking......in what type of case's gravity may not be applied...In static analysis whether the gravity is applicable or not.
  In my case may i do static analysis with out applying graviy or Not....
  wheather the self weight may applicable or Not in Static analysis....
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  - Kumar Dandapani @ Shiva Kumar Bairoju on May 23, 2014 11:59 PM
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    Hi Shiva,
    
    If your considering self weight please add gravity in statci analysis. If your not considering self weight no need to switch on gravity. Thanks
    
    A.D.Kumar,
    EGS Computers India Pvt Ltd
    http://www.egsindia.com
    http://www.egs.co.in
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  - Jerry Steiger @ Shiva Kumar Bairoju on May 27, 2014 2:44 PM
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    Shiva,
    
    If the applied loads in your system are much higher than the gravity loads, then you can usually ignore the gravity loads. For example, if I am designing an electrical contact that applies 100 grams of force on the mating piece and the weight of the contact is just a gram, then I will not bother to include the gravity load in the analysis. In your first post you suggested that the weight of the structure was greater than the external loads. In that case, I would include the gravity loads, unless I had reason to believe that the weight and the external load coupled to the structure in such different ways that I could ignore one or the other. (For example, you had a very tall, slender tower and the external load was pushing sideways on the top of the tower and the gravity load was pulling down along the length of the tower.)
    
    Jerry S.
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Kapil Kumar Apr 18, 2016 8:09 AM
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Hii
There may be cases where you should not apply gravity forces in static analysis...Ex. Suppose there is cylindrical short column (7m dia. and 10m height) fixed at one end. And you want to estimate the URES in x and y directions only that is in plane displacements because of torque applied on top of the column. If you apply gravity, URES is the resultant of the displacement in X, Y,and Z direction, but as you find that because of gravity displacements are very large compared to applied torque, So URES in this case would give wrong estimate. So in such cases it is better not to apply gravity forces to avoid confusion. If you apply no problem but to get in plane displacement you need to check displacements in X and Y separately and then get URES.

Anything wrong...please let me know
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