Confinement factor

03-Analytical/modelling capabilities
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fakharifar.mostafa
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Joined: 06 Jan 2010, 05:34

Confinement factor

Post by fakharifar.mostafa » 09 Sep 2014, 23:56

Thanks SSoft for the great SStruct ver. 7.

However, I have a big confusion. How is the confinement included in this version? Apparently, it does not include unconfined concrete, and my previous models when opened in v. 7, the confinement is automatically updated to 1.2 for unconfined concrete. Also when I change the confinement factor in the material tab and change it from 1.2 to some other value, hit OK, and if open it again it is again reset to 1.2. Why? No matter what you do, it turns to 1.2.

I go to sections tab, and input the confinement factor in Section Characteristics. Then, should I input the confinement here or in the material tab? I want to input the confinement manually, not automatically calibrated. It is not clear in the help system. thanks for clarification.

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seismosoft
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Re: Confinement factor

Post by seismosoft » 10 Sep 2014, 01:48

One new feature in v7 is the specification of the transverse reinforcement. This enabled the automatic computation of the confinement factor for every section type. With respect to v6.5, the following differences have been made:

1) The removal of the confinement factor property from the concrete material models. The confinement factor value in the Material module is located now in the Sample plot groupbox and is only used for monitoring purposes, so that the user sees how the model behaves.

2) The confinement factors for every section region (confined, unconfined, partly confined etc) are automatically calculated in the Sections module, in the Section Characteristics tab. Obviously the user may specify a different value, if he/she desires so.

3) Since the confinement factors are calculated in the Sections module, only one concrete material model may be specified for every R/C section (rcjrs is an exception obviously).

4) In order to ensure backwards compatibility with v6.5 and previous, a typical transverse reinforcement is applied to every section. This should be changed to the correct pattern, in order to get the correct confinement factors.

On a similar issue, note that the specification of the transverse reinforcement has enabled the automatic calculation by the program of the elements' shear and chord rotation capacity (see the two new performance criteria: Frame Element Chord Rotation Capacity & Frame Element Shear Capacity).

For more information please refer to the following two educational videos:
1) SeismoStruct How to create a SeismoStruct model
https://www.youtube.com/watch?v=EkIvZgsJ51Q

2) SeismoStruct Performance criteria
https://www.youtube.com/watch?v=0ZCDciuq4Gg

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fakharifar.mostafa
Posts: 124
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Re: Confinement factor

Post by fakharifar.mostafa » 23 Sep 2014, 20:28

Is there any way that I can somehow find the confining pressure from the transverse reinforcement (i.e., spirals or steel or FRP jacket) to the core fibers? I know fiber based analysis with fibers associated with a prescribed uniaxial stress-strain is incorporated here. I was just wondering if there is any workaround that I could correlate the obtained axial stresses to radial direction at each cross section to calculate the confining pressure from transverse reinforcement. I doubt it, however, worth asking. Thanks.

huffte
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Re: Confinement factor

Post by huffte » 23 Sep 2014, 23:42

Hi fakharifar.mostafa. I would assume that SeismoStruct used the equation for lateral confining pressure from the Mander model, f'l from Equation 19 for circular sections or Equations 27 and 28 for rectangular sections in the original paper by Mander, Priestley, and Park.

You may be asking something totally different, but the paper is usually easy enough to find using a web search on "Theoretical Stress Strain Model for Confined Concrete".
Tim Huff

fakharifar.mostafa
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Joined: 06 Jan 2010, 05:34

Re: Confinement factor

Post by fakharifar.mostafa » 24 Sep 2014, 00:11

Thanks Huffte for the reply.

My bad, I should've been more specific. Indeed, I am not looking for the confined concrete model, as they are referenced by SStruct. I was somehow trying to see that if I could correlate the axial fibers strain into radial direction from the "Output stresses and strains at selected locations" window. I was trying to calculate the dilation of damaged RC column under strong ground motion. Thanks again.

Inzimam ul haque
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Re: Confinement factor

Post by Inzimam ul haque » 27 Feb 2019, 15:15

hello sir...can we model steel strip and cross ties in column is a transverse reinforcement in seismostruct and also can we calculate the confinement pressure value of steel strip and cross ties.

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seismosoft
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Re: Confinement factor

Post by seismosoft » 28 Feb 2019, 18:03

What do you mean with steel strip and cross ties? Note that the introduction of the transverse reinforcement is done in the Sections module.
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seismosoft
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Re: Confinement factor

Post by seismosoft » 28 Feb 2019, 18:04

Note that the confinement factor is calculated automatically based on the provided stirrups (user defined values are also accepted).
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Inzimam ul haque
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Re: Confinement factor

Post by Inzimam ul haque » 01 Mar 2019, 12:42

we use "steel strip+cross ties" instead of conventional stirrup or spiral in column now i want to simulate my results with experimental results... what should i do now?

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seismosoft
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Re: Confinement factor

Post by seismosoft » 04 Mar 2019, 18:21

What you should do is to calculate the confinement factor based on your configuration and specify the value manually in the Sections module, since this not done automatically by the program. Then you will need again to make hand calculations for the shear checks.
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