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Author Topic: Additional Details on Crippling Analysis  (Read 9883 times)

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Additional Details on Crippling Analysis
« on: February 17, 2011, 06:13:02 PM »
Some questions came out about :

- when bending occurs, what is the "applied load" on the element which experience non-uniform load? applied load is linearly varying , what does HS take for load/stress (max, average, 2/3, others)?

- is the correction for bending implemented for both M1 and M2?

- The Crippling report gives correct results but for I beam we would expect to have 5 terms in the calculation. The table is a bit misleading.

- From the Crippling HME it is clear that HS is using Niu generalised methods C. This method is for extruded sections. C sections as well as others can be formed or extruded. We did'nt find any option to specify this detail. Apparently the formed sections are not covered.

- Would you (CRC) be interested in implementing other (simple) crippling methods?


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Re: Additional Details on Crippling Analysis
« Reply #1 on: February 17, 2011, 06:15:42 PM »
1. the applied load for each object in bending is the average compressive load... so if the entire object is in compression, it will be just the average load. If part of the object is in compression and part in tension, the tension part is thrown away and not included in the summation. Then the applied load is the average of the compressive part.

2. I'm not sure about bending in the M2 direction. I actually don't think it is taken into account.  Most of our efforts have gone into stiffened panels where the stiffeners do not bend in the 2 direction.

3. This is sort of related to the last question. The upper flange is actually considered to be one long object for crippling. The right and left sides are lumped together into one. The length that is put into the crippling equation to calculate Fcc will be 1/2 the total width. As long as there is no bending in the 2 direction, this would be equivalent to handling left and right as separate entities, however in 2-direction bending I can see this as causing an inaccuracy. If this is a critical item, it could possibly be changed.

As a side note, when HyperSizer does STRENGTH analyses for the flanges (such as von Mises), it does take 2-direction bending into account, so it evaluates extreme stresses at the tips for example.

4. We do not include separate equations for formed vs extruded. that is true, but we could incorporate. see below.

5. Yes, I think we could incorporate other methods. Would these be items that we could expose to all users or are they proprietary to your company?

If proprietary, we do have a facility for allowing user-defined crippling. It is not something that most engineers can do because it requires a pretty knowledgable programmer and you have to be able to create a Dynamic Link Library.  See this post:
« Last Edit: February 17, 2011, 06:17:48 PM by Phil »