Concrete Filled Steel Tubes (CFST)

03-Analytical/modelling capabilities
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huffte
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Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Concrete Filled Steel Tubes (CFST)

Post by huffte »

For modeling CFST (concrete-filled steel tubes), it seems that there are two options (at least).

First, a composite circular section could be used. In this case, is the concrete considered confined by the tube internally for stress-strain behavior in a pushover analysis? Or are the two materials only made compatible at the interface with no confining effects of the tube incorporated?

Secondly, a jacketed circular section could be used. Again, is the concrete considered confined by the tube internally for stress-strain behavior? Or should I specify an equivalent area of transverse reinforcement to achieve the confining effect.

Thanks as always. - Tim
Tim Huff
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seismosoft
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Joined: 06 Jul 2007, 04:55

Re: Concrete Filled Steel Tubes (CFST)

Post by seismosoft »

Hello Tim,

In the first case the concrete confinement is automatically calculated by the program, considering the effect of the steel tube. You can see the value of the confinement factors in the Section Characteristics tab of the Edit Section Parameters form (accessed from the Sections module). Even with minimal reinforcement the confinement factor assumes large values
In the second case though, if you employ an equivalent circular jacketed sections, you need to calculate the equivalent area of transverse reinforcement to achieve the confining effect.
I think that the first option is superior for your modelling.

Best Regards,
Seismosoft Support
huffte
Posts: 939
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Re: Concrete Filled Steel Tubes (CFST)

Post by huffte »

Perfect. That is exactly what I needed to know! Thanks so much.
Tim Huff
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