Define yielded rebar in materials

[Mohammad_Vali]

Dear Sir/Mad
Hello
I want to define yielded steel as a material (because of modelling RC Frame with yielded rebar), how can i define it? in other words wich is the best way to define and model yielded rebar?
Thanks a lot

[z.gronti]

Dear Mohammad_Vali,

I am not sure that I understand what you want to model. The steel rebars yield when their yielding strain is reached. What do you mean by model yielded rebar?

[Mohammad_Vali]

Dear Zoi Gronti
I mean the definition of a steel that has reached its yield strength due to previous loading and has no tensile strength, I want to define and model this low-strength steel and do the analysis again and compare the results with the first analysis

[huffte]

I think more clarification is needed Mohammad_Vali. A yielded rebar still has tensile strength. If it has no tensile strength (presumably, has fractured) then it would not be in the model anyway.

[Mohammad_Vali]

Dear Zoi Gronti
yes you are right,please help me to define a steel material that has reached to yielding strain and has low tensile strenght.
For modeling low-strength steel that has reached the yield point, I did a method in which I reduced the elastic modulus of the steel from 200GPA to 0.1GPA , but the time history analysis is not complete and gives an error (fbd-tol & ...), so I ask you for a better way.

[seismosoft]

Mohammad_Vali,
It is not clear what you are trying to do. Note that any model has no loads at first (i.e. before applying the loading), and even if it has a very low tensile strength or modulus of elasticity it cannot be yielded by default.
Seismosoft Support

[ESTRUCTO]

Hi.

I want to compare a SAP2000 Pushover example analysis with the same example using SEISMOSTRUCT Pushover analysis, but I am not really sure how to introduce the ASCE 41-17 Table 10-1 FACTORS TO TRANSLATE LOWER-BOUND MATERIAL PROPERTIES TO EXPECTED STREGTH MATERIAL PROPERTIES:

Concrete: 1.50
Reinforced Steel: 1.25

I have used MANDER (Concrete) and BILINEAL (stl_bl) models in SEISMOSTRUCT.

Both capacity curves are similar in shape, but the SEISMOSTRUCT V values are lower than obtained using SAP2000, and I think that this could be the problem, how to introduce this factors to expected strength of the materials correctly.

Thanks in advance.

[z.gronti]

Dear ESTRUCTO,

The strength values assigned in the materials' properties are those used in the analysis.

[ESTRUCTO]

Thanks a lot.

ASCE 41-17 (10.2.2.1.2) indicate "Nominal material properties, or properties specified in construction documents, shall be taken as lower-bound material properties. Corresponding expected material properties shall be calculated by multiplying lower-bound values by a factor taken from Table 10-1 to translate from lower-bound to expected values. Alternative factors shall be permitted where justified by test data."

So, I have defined f´c nominal value as LOWER BOUND STRENGTH. If I would like to reproduce this material expected properties for the analysis, Where should I define this ASCE 41-17 expected strength value (f´c * 1.50)? Same for reinforced steel material (Longitudinal and transverse). I have compared the pushover analysis results using SAP2000 and SEISMOSTRUCT, and SAP2000 capacity curve values are higher than those obtained with SEISMOSTRUCT, and I think that this expected strength values definition could be the problem, because they were defined in SAP2000 but not in SEISMOSTRUCT. Same values in both softwares for plastic hinges, loads, etc. The structural performance is similar in both analysis, with similar displacement values, but the maximun V values in the capacity curves are different a lot.

Thanks.

[z.gronti]

Dear ESTRUCTO,

In the material properties, the lower-bound strength and the mean strength are available. The mean strength is the result of the multiplication of the lower-bound strength with the factors you mentioned. In the Code-based checks, the values required by ASCE 41 are used, i.e. the mean strength for the Chord rotation checks, and the lower-bound strength in the Shear capacity checks.