UCSD Column with Rotational Spring at base.

[shahnewaz]

Hi,

I will really appreciate if someone could help me to find the problem in my modelling a UCSD blind prediction column. This is also available in Seismo verification manual.

I tried to model the column with a rotation spring at base to check how the link element as a spring works in seismo. However, I could not figure out the problem in my model.

1. I created three nodes (1,2,3, where 1 and 2 are the same coordinate at base.
2. I created rotational spring by linking node 1 and 2 with a zero length element. I used bi-sym model. The spring constant comes from the moment curvature.
3. Then I created a elastic frame element between node 2 and 3 and put the lumped mass on node 3. Properties of this elastic element I considered from the X-sectional geometry of the column.

Then I run static pushover and nothing happen, column is too stiff and not moving. The link element is not working.

I attached my model. Someone please guide me to find the error.
Thanks

http://www.4shared.com/file/tmA_8GFlce/USCD_Column.html

[salar]

Send me, your full issue as pdf or word to describe more about modeling. I don't know, what is your modeling!

[huffte]

Hi shahnewaz.

Make certain that your spring data is correct. Note that SeismoStruct requires input of moment-rotation values in the link properties, not moment-curvature.

If you'll e-mail your model, I'll take a look at it and respond with any findings along with some simple models I have constructed with link elements. The link you provide raises security concerns from my anti-virus software, hence the request for the e-mail.

Best of luck.

[shahnewaz]

Thank you huffte and Salar. I send my model in your email.

[huffte]

shahnewaz, I have two observations:

1. your linear link spring constants - besides M2, which you have set to your desired values in a nonlinear element - were all very small, and I believe they should be very large. I changed them to large numbers - take caution here and read the Help System regarding the assignment of large artificial stiffness values

2. I had to increase your target displacement in order to get the link to yield. I increased it from 2 to 7.

I'd recommend making sure your properties are the appropriate values.

Best of luck shahnewaz.

[shahnewaz]

Thank you Huffte. Yes, now it works. I restrained my link in other direction (except M2) by giving large spring constant.

[1MS18CSE25]

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