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[Xansys] [STRUC] [WB] Pre-deformation to a Steel Member IPE3
 
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saroj.kumar.jha
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Joined: 03 Jun 2015
Posts: 7

PostPosted: Fri Jul 31, 2015 8:26 pm  Reply with quote

Dear Vinod,

Your analysis settings seems ok to me. And if you have applied the uni axial force then the reaction force in load application direction at buckling point is the collapse load . I think you have applied uni axial compression load on your structure.

About sub steps, it won't have much effect on your effect as your structure is simple. Sub steps are used for load increment during non linear analysis. Smaller sub step means smaller load increment, so that we can capture non linear behaviour more accurately.
As per your UPGEOM command syntax what I understand that you have amplified the linear buckling modes by 5 factor. Once try with higher amplification means higher initial imperfection . May be the initial imperfection is very small in comparison to your structure that's why there is no effect of sub step size. And please include material non linearity if you have not included. Material non linearity is also an important factor in non linear buckling.

Any ways if your structure is quite robust to applied load, then sub step size won't have much effect on non linear buckling.

Can you please tell me about your structure dimensions and applied load? It will help in analysing the results.

Hope this will help you. Have a nice weekend.


Regards

Saroj Jha
Engineer, CRVV
ITER-India

Sent from my Windows Phone
From: vinod kumar ramamurthy
Sent: 29-07-2015 PM 11:47
To: ANSYS User Discussion List
Subject: Re: [Xansys] [STRUC] [WB] Pre-deformation to a Steel Member IPE300



Dear Saroj Jha

Yes I used my deformed geometry from FE Modeler into Non Linear Static Structure analysis and also I included the Large Deformation settings ON in analysis settings tree.

/prep7

UPGEOM, 5, 1, 1, buckling, rst

cdwrite, db, buckling, cdb

how can i find the total collapse load for the model?

What I get now is a load of 6524.5 N in Y - Axis.
i.e Minimum value over Time is 652.18 N and Maximum value over Time is 6524.5 N.

1. Initial the Step Controls.
Number of steps - 1
Current Step Number -1
Step End Time - 1s
with Auto Time Stepping ON
Define by - Time
Initial Time Step - 0.1s
Minimum Time Step - 0.1s
Maximum Time Step - 1s

When I change the time to 25secs, I get the same load of maximum and minimum value which I mentioned above clearly!!!

Does that mean, 6524.4 N is my total collapse load for the model irrespective of the step controls I alter ???

Vinod Kumar Ramamurthy
Bauhaus-Universitšt Weimar(NHRE)
vinod.kumar.ramamurthy@uni-weimar.de
www.uni-weimar.de
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vinod.kumar.ramamurthy
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Joined: 24 Jun 2015
Posts: 10
Location: Weimar, Germany

PostPosted: Sun Aug 02, 2015 2:28 pm  Reply with quote

Dear Saroj Jha

Yes I have include the Non-Linear Material (Structural Steel NL) from the engineering data and used it for only during Non-Linear Analysis after giving geometric imperfection to the model.

Like you said I will increase my amplification for imperfection and run the analysis again.

I have shared you the dimensions for the structure below.

I have chosen an IPE300 Section as a model. For this section I have modeled the beam element, shell element, volume element. I have extruded the structure to a length of 1000mm in X-Direction.

For Volume Element below I have provide you the details you asked for.

Boundary Conditions:

For Static Structural before imperfection applied:

Fixed Support at one end, Displacement at the other end with only X-component free, Y&Z-component constrained.

Remote Force of 1N (compressive) at the same send as displacement condition provided. i.e. @Coordinates 1000,0,0

Linear Buckling - Max Modes to find - 10

Boundary Conditions Non Linear Analysis:

Fixed Support at one end, Remote Displacement of -1 mm in X-component @Coordinates 1000,0,0

Remote Force of 1N (compressive) at the same end as displacement condition provided. i.e. @Coordinates 1000,0,0

Your previous was so much helpful for me to understand the concepts. Have a nice weekend.

Regards
_________________
Vinod Kumar Ramamurthy
Bauhaus Universität - Weimar, Germany
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