Seismosoft | Earthquake Engineering Solutions

Hi
How can I model CFT column ( concrete filled tube ) in SeismoStruct

Dear aliisaberiiii,

There is a number of composite sections available in SeismoStruct. Probably the Composite rectangular or circular section might cover your modeling requirements.

z.gronti wrote: 14 May 2021, 09:18 Dear aliisaberiiii,

There is a number of composite sections available in SeismoStruct. Probably the Composite rectangular or circular section might cover your modeling requirements.

Unfortunately it does not exist.
Can two sections be used for one column at a time? One is a steel rectangle hollow section (rhs) and the other is a concrete rectangle solid section (rss)

Dear aliisaberiiii,

Could you please explain what do you mean by "it does not exist"? The sections I mentioned are available in SeismoStruct v2021.

Yes, you may use two sections, as you described, connected to the same two end nodes.

z.gronti wrote: 14 May 2021, 10:59 Dear aliisaberiiii,

Could you please explain what do you mean by "it does not exist"? The sections I mentioned are available in SeismoStruct v2021.

Yes, you may use two sections, as you described, connected to the same two end nodes.

Dear z.gronti,
There are only composite sections with reinforced concrete(fig.1), but my section is a CFT column with unreinforced concrete. As in Figure 2
Now my question is how can I model this column(fig.2)

Could you not use the 'css' section and remove all longitudinal reinforcement? And you could set the transverse hoops to something extreme (say, 2mm bars spaced at 2 meters) to effectively eliminate their influence. It seems you could further reduce the influence of any reinforcement by specifying the reinforcing material to have an extremely low E (say 1 psi) and and extremely low fy (say 1 psi).

These are just ideas off the op of my head and I am uncertain if they would work. I haven't tried them but it might work. There could also be some internal, mathematical stability issues, not sure. But don't give up. I think it might suffice.

huffte wrote: 14 May 2021, 13:55 Could you not use the 'css' section and remove all longitudinal reinforcement? And you could set the transverse hoops to something extreme (say, 2mm bars spaced at 2 meters) to effectively eliminate their influence. It seems you could further reduce the influence of any reinforcement by specifying the reinforcing material to have an extremely low E (say 1 psi) and and extremely low fy (say 1 psi).

These are just ideas off the op of my head and I am uncertain if they would work. I haven't tried them but it might work. There could also be some internal, mathematical stability issues, not sure. But don't give up. I think it might suffice.

Thank youu

huffte wrote: 14 May 2021, 13:55 Could you not use the 'css' section and remove all longitudinal reinforcement? And you could set the transverse hoops to something extreme (say, 2mm bars spaced at 2 meters) to effectively eliminate their influence. It seems you could further reduce the influence of any reinforcement by specifying the reinforcing material to have an extremely low E (say 1 psi) and and extremely low fy (say 1 psi).

These are just ideas off the op of my head and I am uncertain if they would work. I haven't tried them but it might work. There could also be some internal, mathematical stability issues, not sure. But don't give up. I think it might suffice.

Hi,
Can you advise me about Modeling Parameters and Acceptance Criteria for Nonlinear Procedures - CFT columns (unreinforcement)?
I want to model the Hinges for nonlinear analysis but I can not find their parameters in FIMA356 or ASCE41. The parameters are only available for steel and concrete structures and not for composite columns.

For bridge structures using CFT, AASHTO specifies an in-ground, analytical plastic hinge length of (0.1H1 + 1.25D), but no greater than 2D. H' is the distance from the ground surface to the point of contraflexure. D is the diameter of the tube.

For acceptance criteria, the compressive strain in the tube could be limited to [10/(D/t)^(2)] to capture local buckling of the tube. This strain limit is from "Proposed Pipe Pile Strain Limits for ASCE 61-19", Harn & Pitarkis, 2019. The Port of Los Angeles has design documents with different strain limits, but they presumably do not account for potential local buckling.

I would suggest a further review of the literature to pinpoint your desired modeling criteria and strategy, a matter primarily to be determined by yourself and your supervisor.

Hi. I wanted to know if it's possible in SeismoStruct to determine whether a non-compact CFST column is failing due to local buckling rather than global buckling. I understand that stress points can be monitored, but they don't explicitly indicate failure. Even when the ultimate strain of steel is exceeded, the software doesn't seem to identify the failure point due to local buckling.
Can anyone tell me how I can find when non-compact section is failing due to local buckling in seismostruct?