Problem with the Chang-Mander concrete model

[ashtari]

It seems that when using Chang-Mander concrete model in SeismoStruct, it does not apply the confining effects to the concrete core fibers. Therefore, the stress-strain response of the cover concrete is the same as the outer fibers of the core concrete. There is no such issue with the Mander model. Is it a bug in the code, or otherwise how I should I take care of this?
(Seismostruct takes only one material for each concrete section, and assign one section to each element, so I cant define confined and unconfined parts separately)

[z.gronti]

Dear ashtari,

Please refer to the following topic:
http://www.seismosoft.com/forum/viewtop ... ent#p11787

[ashtari]

Dear Gronti,

I am aware of what SeismoStruct is supposed to do. But, for this material model (Chang-Mander), if you check the stress-strain of confined and unconfined concrete they both are similar to unconfined concrete, while using Mander model they are different. Could you check this problem?

Thanks

[z.gronti]

Dear ashtari,

I couldn't reproduce the reported error. Could you please make sure that the confinement factor of the section you check with Chang-Mander model is greater than 1? Also, could you please check if you have assigned the correct stress points for the confined and unconfined concrete?

[ashtari]

The confinement factor in the plastic hinge region is 1.27 and it is automatically calculated. The stress points are fine too. I mentioned earlier, I am running the same model, the same stress-points, and I just change the material model type. The Chang-Mander model unlike the Mander model does not apply the confinement factor inside the software code. I need to work with the former, since it has more parameters to define the model.

[z.gronti]

Dear ashtari,

Would you like to send me the model at z.gronti@seismosoft.com to check it?

[z.gronti]

Dear ashtari,

Thank you for reporting the bug. There is a bug in the current version only in the stress points and only for the Chang-Mander model. I would like to point out that the confinement factor of the section with Chang-Mander concrete model is correctly taken into account during the analysis and only for the stress points it is not properly taken into account.
The bug will be corrected in the next version of SeismoStruct that will be released in about 3 months.