The initial stiffness of the SteelBRB material seems to be incorrect. See image here:
http://imgur.com/a/7FDdQ
The black is from the curve published in "Elastoplastic model for steel buckling restrained braces" (Alessandro Zona, Andrea Dall'Asta, 2012) and the red is the OpenSees output with the parameters from the paper. It matches well everywhere except the initial cycle where the tangent stiffness is not equal to E. I was curious if anyone else has experienced a similar behavior when using this material.
SteelBRB Initial Stiffness
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edwardal
- Posts: 20
- Joined: Wed Aug 24, 2016 5:33 am
- Location: Istituto Universitario di Studi Superiori (IUSS)
Re: SteelBRB Initial Stiffness
Upon further investigation, it seems that if you want the "sharpness" in the initial stiffness, you also need the sharpness in the higher displacement cycles.
http://imgur.com/a/402Ac
The above image has the same parameters listed in the paper with the exception of the alpha+ (alpha_T) value which was changed from 0.6 to 10.0. The initial stiffness is well represented, but the higher displacement tension cycles are not as realistic. Maybe the behavior I am looking for is not possible with this material, but if anyone knows otherwise please let me know.
http://imgur.com/a/402Ac
The above image has the same parameters listed in the paper with the exception of the alpha+ (alpha_T) value which was changed from 0.6 to 10.0. The initial stiffness is well represented, but the higher displacement tension cycles are not as realistic. Maybe the behavior I am looking for is not possible with this material, but if anyone knows otherwise please let me know.