A question about asymmetric-Takeda Curve for RC joints

[Ahil_Anand]

Hi Seismosoft,

I have a question about modeling of a RC joint. I want to create a RC joint model, based on the verification report of seismosoft (CH.4, Example RC joint). In the report, there was a symmetric beam which was connected to a column. for the joint, symmetric Takeda curve was used and the springs parameters were calculated based on these symmetric sections. My RC joint model, has a asymmetric beam which is connected to a RC column. Please help me for these two questions:
1- Should I use asymmetric Takeda behavior curve from the seismostruct for the beam?
2- When I want to calculate the springs parameters for Takeda curve, I which direction should be consider? I mean that in surface of the beam which is connected to the joint, the moment is negative and the upper reinforcements are in tensile. When I want to define five parameters of the Takeda curve, I only can define one curve (not for positive or negative direction separately). I don't know which one (upper reinforcements in tensile or lower reinforcements in compression) should be used to calculate the springs parameters (Tackeda parameters). There were a lot of papers about RC joint modeling, but all of them were used other softwares like openness. Because of this, I only can ask my questions from your forum.

[seismosoft]

Hi Ahil_Anand,

1. Yes for asymmetric sections one should employ the asymmtric Takeda curve
2. It is not clear what you mean. The DOFs of the link element are well-defined in the manual and the help system of the program. Note that the positive branch of the curve, corresponds to the positive direction of corresponding axis. Further, note that any link element of any software is defined in the same way as the link elements in SeismoStruct. Hence, one can read any paper that employs another program, and get guidelines to do the modelling in SeismoStruct or any other package.

Seismosoft Support

[Ahil_Anand]

I see new posts in the forum about joint. These posts were helpful to me. Thanks to have this forum with a lot of suitable topics.
First of all, thanks for your answer about my first question. For the second one, I can calculate all of spring parameters such as yield and ultimate strength and also, yeild and ultimate stiffeness. But these values are different for upper bars(tensile bars) and lower bars (compression bars). Takeda asymetric curve, need two yield strengh and only one stiffeness. I am confused that for the end of the beam which is in negative bending, I should be define Yield and ultimate strength and stiffeness for tensile bars which are located at the top of the beam? And for other Fy, I should be define yield strength of the compression bars which were licated at the bottom?
I also want to know that all of these parameters should be define in the program without - sign? It means that all of them should be difibe +?

[seismosoft]

Please refer to the description of the curve in the program's help and users manual.
There you will be able to find details on the definition of all the curve parameters. A strength of 400kN in the negative axis, obviously means that the yield limit
is -400kN. Regarding the stiffness, indeed it assumes a positive values because it is multiplied by negative deformations to derive negative forces.

Seismosoft Support