Stress exerted on pipe column face by base plate stiffener??? 4

[ST04]

Hi

I was looking for a reference to determine the Stress exerted on column face by base plate stiffener, the base plate stiffener that I'm talking about is similar to this:

http://www.fhwa.dot.gov/bridge/images/sign36.jpg

I have only found an equation in "Design of Monopole bases" page 77. But the result is relatively small around 30 N/mm^2.

The problem is that when comparing the hand calculation with the Ansys FE model I'm getting larger stresses and ends up with the upper edge of the stiffener connected to column face is overstressed as well as the column surface at that point.

For the constrains in the Ansys I have tried both cases of making stiffener connected to the column as an assembly and then put "Bonded" contact constraint and tried to make the column and stiffeners as one part then connect them to the base plate, but in both cases I'm getting what is stated above.

So either the hand calculation is not conservative, or the Ansys analysis is not giving accurate values.

Any suggestions?
Thanks

 

[paddingtongreen]

@dhengr,
I was thinking the same thing, but we were not raised on these programs. I had difficulty in the nuclear power business making the models run without these nonsensical results. I knew the structure was good when I created it, but I had to make the model results agree or my design was condemned.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[BAretired]

dhengr,

Continuing the stiffeners through the HSS reduces bending stress on the wall to nearly zero. No need for ring thickening or other expensive methods.

BA

 

[ST04]

Hi dear colleagues thanks a lot for your valuable inputs

Dear dhengr
I enjoyed reading your comment, it looks like you do like FE (Just kidding).

Well, I used Ansys for such non-complicated design considering the values provided by the software to be something close to what would happen in real experimental test (which is not always possible to be done). Also I wanted to verify the accuracy of the results because I have other cases with moments.

I'm concerned about the stresses although there are several factors of safety in both materials and loads because having overstressed structure could cause the structure to collapse as stress is just another way to interpret the applied loads. What is the use of the structure if the base goes in failure!

Regarding the shape of the stiffener, there is a valid point to have such shape, as if you use for example a rectangular stiffener, the extra part other than shown in the picture will have almost 0 stress and I have tried several sizes and arrangements.

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Dear BAretired and hokie66
I have tried to do such arrangement and it does reduce the stresses for the continuous stiffeners but others won't have much reduction.

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Dear hokie66
If there were no stiffeners there would be green then yellow at the top, but due to stress concentration at the top end of the stiffeners a yellow zone will appear as shown then it will become green when the influence of the stiffeners reduces then it will be yellow again as it is approaching to the end of the column section in the model.

Thanks every body, I have an idea maybe it will solve the concentration problem, will be back soon...
Regards