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Non-linear static analysis LGDISP with multiple loads

Creator
Creator

Hello,

I'm trying to conduct a non-linear anlysis with large desiplacement to analyse a helideck on a ship for crash landing loads combined with other loading like ship structure selfweight and hydrostatic pressure due to sea loads. As the sequence of the these loads is very important to get accurate results, in this case the ship will be subjected to its selfweight and hydrostatic pressure before the heilcopter crash landing loads. I am farily new to FEMAP and doing Nonlinear analysis, what is the best approach to conduct this kind of analysis? 

Thanks

3 REPLIES

Re: Non-linear static analysis LGDISP with multiple loads

Siemens Phenom Siemens Phenom
Siemens Phenom

If you are using SOL 106 nonlinear statics, then the subcases are actually a loading history. Each subcase should specify the total load load desired, Nastran will internally find the change in load from one subcase to the next and apply that change so you end up with the total load specified in the subcase. In Femap create 3 load cases, each one being the total load desired for that particular subcase.

 

So to create the scenario you describe:

 

SUBCASE 1    $ apply gravity

LOAD=1

 

SUBCASE 2  $ add other loads to gravity

LOAD = 2 

 

SUBCASE 3  $ add crash load to other loads

LOAD=3

 

 

Regards,

 

Joe

Re: Non-linear static analysis LGDISP with multiple loads

Creator
Creator

Hi Joe,

 

Thank you for your response. Please excuse my ignorance, but I'm fairly new to FEMAP and nonlinear analysis so if you can please elaborate little bit more and how this is done.

I am using the SOL 106 nonlinear static, initially I just had one load case with crash load as elemental load, gravity as body load and hyrdostatic load as elemental load. below is is my nonlinear analysis options.

But now that I found a DNV guidance on Nonlinear analysis that points out the importance of load sequence.

 

 

Capture.JPGloading.JPG

Re: Non-linear static analysis LGDISP with multiple loads

Siemens Phenom Siemens Phenom
Siemens Phenom

Once you have created the a load case for the total load required for each subcase, then go to Analysis Set Manager to create the subcases:

Highlight the "no cases defined"; then click on "new"

2017-08-31 09_17_15-Analysis Set Manager (Active_ 1..multi subcase).png

Set the the desired loads in the boundary conditions of each subcase. You can also change iteration strategy settings for each subcase:

 

2017-08-31 09_23_43-Analysis Set Manager (Active_ 1..multi subcase).png