Pushover with confined concrete

[asmith]

Hi,

I am attempting to do a pushover analysis of a single bay, two storey tall RC structure. I will do this as a bare structure and with FRP confinement. My pushover for the bare frame is good, but I am struggling with the FRP confinement. There are numerous materials available (confinedconcrete01, FRPConfinedConcrete01 + FRPConfinedConcrete02), but these gives poor results with extremely unstiff structures. Even the examples for these materials are unrealistic. I am slightly concerned these materials don't function properly because of the periods and displacements they give.

Does anyone have any advice on what material i may be able to use? Not sure if anyone has tried to do this yet.

Many thanks

[ismailqeshta]

I have tried both FRPConfinedConcrete and ConfinedConcrete01, and they showed similar results. However, I would recommend ConfinedConcrete01, as it requires less info. It has been used in many studies over the past few years.

[asmith]

Hi ismailqeshta,

Have you compared these to say concrete02, because when I switch materials my periods increase greatly to unrealistic values. Even the examples of FRPconfinedconcrete do not run properly. Do you have this problem? I also have problems with ConfinedConcrete01, where the period increases greatly and the capacity of the structure greatly decreases.

If you have any simple examples of this in operation, would you mind sharing them with me to see if they work? I really think the materials are not functioning because of a problem with my program.

Thanks

[ismailqeshta]

ConfinedConcrete01 is based on Braga and Laterza (2006) model, while concrete 02 is based on Yassin (1994) work. Hence, they would definitely show some differences in behaviour.

Regarding your period change, why don't you just test whether you run the model correctly by following the examples given the ConfinedConcrete01:
http://opensees.berkeley.edu/wiki/index ... 1_Material

I started by following these examples, and gradually got a sense of every input parameter. Feel free to ask me about any of them.

Regarding FRPConfinedConcrete, I honestly can't remember exactly which example I followed, but I think the one provided on the page worked with me.

I am sure there is something wrong in your input of the parameters in both models, which leads to the change in period. You may start off by doing it for the uniaxial test to make sure, from the stress-strain curves, that you get the model right, like in the examples given in the link above.

[selimgunay]

If you have problems with the confined cincrete materials, you can compute the confined concrete parameteres and use concrte02 or concrete04 using confined concrete stresngth and strain values.