which uniaxialMaterial can be used to define damping

wangjingze1985 · Post by **wangjingze1985** » Mon Dec 06, 2010 11:57 pm

I want to use the Zero-Length Element to define a damping element,
BUT I do not know which uniaxialMaterial can be used to define damping .
anyone can help me?

vesna · Post by **vesna** » Tue Dec 07, 2010 3:11 pm

I do not understand your question. Do you want to assign damping to an element or yo want to define damper?

wangjingze1985 · Post by **wangjingze1985** » Wed Dec 08, 2010 12:46 am

I want to define a damper, a friction damper.

I think the Zero-Length Element can be used. BUT I do not know which uniaxial can be used to define the envelope. enve worse, I can not copy the picture which can show the envelope to here.

My English is very poor , I think it may caused some troubles for you to understand my words. BUT I relly need some help, can you help me ?

vesna · Post by **vesna** » Wed Dec 08, 2010 3:57 pm

Try posting your hysteretic curve at www.4shared.com. After you post it there send me the link so I can see the shape of your hysteretic model.

wangjingze0720 · Post by **wangjingze0720** » Wed Dec 08, 2010 9:50 pm

Think you for your patience.

The link is www.4shared.com/document/wsXbRrvu/1_online.html
Open the file you download and you can see the hysteretic curve which can show the force and deformation relation of the material.

The force in Y axis and deformation in the X axis. the file was editored by Microsoft Excel 2003.

wangjingze0720 · Post by **wangjingze0720** » Wed Dec 08, 2010 9:51 pm

the file named "ï¼ˆå

vesna · Post by **vesna** » Thu Dec 09, 2010 10:11 am

You only showed me the positive side of force-displacement relationship. What happens on the negative side?

The only materail in OpenSees that is capable of capturing material hardening is Bouc-Wen Material:
http://opensees.berkeley.edu/wiki/index ... n_Material

You will have to play with the parameters to get behavior that you want. Generally, the hysteresis loop will exhibit hardening if Î²+Î³ < 0 and Î²-Î³ > 0 (e.g., Î²=0.25 and Î³=-0.75).

If not familiar with Bouc-Wen Material check the references.

wangjingze0720 · Post by **wangjingze0720** » Thu Dec 09, 2010 11:50 pm

Thank you very much.

The material is similar to rubber or concrete, the positive side of force-displacement relationship can be ignored. In fact, the file you saw has something wrong: it showed the negative side of force-displacement relationship not the positive side. Compressive load should be input as negative value.

I am a chinese student. I can not got the two references.

Baber, T. T. and Noori, M. N. (1985). "Random vibration of degrading, pinching systems." Journal of Engineering Mechanics, 111(8), 1010-1026.

Wen, Y.-K. (1976). \Method for random vibration of hysteretic systems." Journal of Engineering Mechanics Division, 102(EM2), 249-263.

wangjingze0720 · Post by **wangjingze0720** » Thu Dec 09, 2010 11:51 pm

Thank you very much.

The material is similar to rubber or concrete, the positive side of force-displacement relationship can be ignored. In fact, the file you saw has something wrong: it showed the negative side of force-displacement relationship not the positive side. Compressive load should be input as negative value.

I am a chinese student. I can not got the two references.

Baber, T. T. and Noori, M. N. (1985). "Random vibration of degrading, pinching systems." Journal of Engineering Mechanics, 111(8), 1010-1026.

Wen, Y.-K. (1976). \Method for random vibration of hysteretic systems." Journal of Engineering Mechanics Division, 102(EM2), 249-263.

wangjingze0720 · Post by **wangjingze0720** » Fri Dec 10, 2010 1:43 am

Look at the hysteretic curve of the material, when the deformation increased, the stiffiness increased. I think this is very important and Bouc-Wen Material can not fit this.

Is there some other materials can fit this?

vesna · Post by **vesna** » Fri Dec 10, 2010 10:55 am

Bouc-Wen can capture material hardening, but the hysteresis will have values on both sides (positive and negative) and can not be applied to your case.

Unfortunately, there is no material that can fit the material you have. The only way would be to write your own material. In case you do it please share it with the OpenSees community.