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Author Topic: Limit and Ultimate Load Factors for Components and Load Cases  (Read 8830 times)

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Limit and Ultimate Load Factors for Components and Load Cases
« on: October 22, 2008, 02:25:59 PM »
On project set up sheet-->load sets we have ultimate and limit load factors. Also, in Project sizing sheet-->design to loads under the factors we have mechanical limit and mechanical ultimate.

So, it seems to me if I import a FE model into HYPERSIZER, I get to set ultimate and limit load factors in two places. My first question is what about if the factors specified in these two places are contradictory (in one place I specify ultimate load factor=1.5 and in the other place ultimate factor=1)?

I also wanted to make sure that if:

limit load factor=1 and ultimate load factor=1, then limit and ultimate MS are equal. Right?
Also, if limit load factor =1 and ultimate load factor=0, they we only get limit MS back. Right?

Phil

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Re: Limit and Ultimate Load Factors for Components and Load Cases
« Reply #1 on: October 22, 2008, 02:26:18 PM »
1. The load factors from the Project Form | Setup Tab are cumulative with those on the Sizing Form | Design-To Loads tab.  This way you can have independent control over whether load factors are based on each component or if they are based on load cases.

If you specify an ultimate factor of 1.5 on the Project Form and 1.5 on the sizing form, you will ultimately get a load factor of 1.5 * 1.5 = 2.25

2. If limit and ultimate load factors are both 1.0, then you will get the same margins for limit and ultimate... with one exception.  Metallic materials use yield allowables for limit loads and ultimate allowables for ultimate loads, so you will see different limit and ultimate margins for metallic strength failure modes. 

3. If either limit or ultimate factors are set to 0, then you will get no margins for those load.  So the answer to this questions is yes.

garyjh

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Re: Limit and Ultimate Load Factors for Components and Load Cases
« Reply #2 on: March 29, 2011, 05:32:37 AM »
Further to previous discussion, I have imported an FE model with loads that are ultimate with an ultimate factor of 1.5 applied in the FE model. Therefore, to get limit and ultimate loads in Hypersizer in the Project Form | Setup Tab the mechanical limit factor was set to 0.666 and the ultimate limit factor set to 1. In the Sizing Form | Design-To Loads tab both the mechanical limit & ultimate limit factors were set to 1.

However, when carrying out composite unstiffened plate and sandwich foam panel buckling, material strength composite ply and sandwich analyses the limit & ultimate MS's are the same. This implies that the imported ultimate loads have not been multiplied by the project limit factor 0.666 x design-to loads limit factor 1 to give an overall limit factor of 0.666.

Any help on this would be appreciated. Thanks.

James

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Re: Limit and Ultimate Load Factors for Components and Load Cases
« Reply #3 on: March 29, 2011, 12:34:35 PM »
Gary,

I have tested this and it seems to be working properly. Can you confirm that the Controlling load set has a limit load factor set to 0.667 on the load sets tab. Once you change the load factors on the Setup form | Setup tab, you will have to select "Save" at the top of the Setup form.