Seismosoft | Earthquake Engineering Solutions

Hi
I'm doing a research on an 8 storey RC frame. Transverse reinforcement in this frame is complied regarding to ACI318-08. Transverse reinforcement in the special joint area (regarding to ACI) is spaced every 100 mm. On the remaining part of beams and columns rather than special reinforcement detailing area, transverse reinforcement are spaced every 200 and 150 mm for beams and columns respectively. Due to this reinforcing detail through elements, I'm applying con_vc.
Every time I run Adaptive pushover Analysis on this frame it diverges prematurely. It is noteworthy to mention that with the utilization of con_cc, this problem doesn't happen and Adaptive Pushover converges really fine. I have also set Tensile Strength (ft) of concrete equal to zero regarding to the SeismoStruct Manual suggestion for numerical stability. It didn't work either.
Now I send the file to your email for further consideration by your respectful company.[:)]

Hi there,

Unfortunately, and as stated in the Help System, the con_vc material model is very numerically demanding, and its use in advanced analysis algorithms (such as adaptive pushover) may indeed give rise to numerically difficulties (apart from rendering the analysis much slower).

We paid, in any case, a look into your model, and noticed that the analysis runs to an already significant deformation level (e.g. the displacement-shear curve is already on its softening branch and the strains in the concrete exceed values of 0.006). Hence, the analysis is actually progressing well within the nonlinear inelastic range, probably beyond code-type ultimate limit states.

Seismosoft Support

Dear SeismoStruct Instructors
Thanks for your prompt contribution. But If you consider Ultimate lateral displacement (Delta U) under adaptive pushover compared with con_cc applied material you would probably see significant difference between con_cc and con_vc. This point would cause considerable effect on the results when ductility factor (R) is under attention. Therefore I would want to ask what is the main cause of this difference? Because the time I apply con_cc for concrete material, I attain higher values of capacity curve compared to con_vc. What is the main cause of this difference?
Thanks

quote:Originally posted by fakharifar.mostafa

Dear SeismoStruct Instructors
Thanks for your prompt contribution. But If you consider Ultimate lateral displacement (Delta U) under adaptive pushover compared with con_cc applied material you would probably see significant difference between con_cc and con_vc. This point would cause considerable effect on the results when ductility factor (R) is under attention. Therefore I would want to ask what is the main cause of this difference? Because the time I apply con_cc for concrete material, I attain higher values of capacity curve compared to con_vc. What is the main cause of this difference?
Thanks

Dear Fakharifar Mostafa,

Your question is on earthquake engineering, rather than on SeismoStruct issues, hence this is really not the right venue for such a discussion.

In any case, we can tell you that we will be surprised if the use of 'con_vc' leads to a significant variation of displacement capacity of a full frame structure, with respect to when 'con_cc' is instead employed. You are not confusing structural ultimate capacity with analysis end displacement, are you? The former is related to the attainment of certain performance threshold values (e.g. material curvatures, chord rotations, storey drifts), whilst the latter may be simply a reflection of numerical convergence/stability.

Finally, we suggest to you that, in order to understand better the influence that different material constitutive relationships have on the results of a given analysis, you may (i) read the scientific publications where such the latter are presented and (ii) carry out sensitivity studies on simple models (e.g. single cantilever).

Seismosoft Support