Defining a Zero length Fiber cross section -

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chhareen@STKO
Posts: 4
Joined: Fri Jul 02, 2021 10:47 am

Defining a Zero length Fiber cross section -

Post by chhareen@STKO » Mon Nov 29, 2021 6:19 am

Dear STKO Team,

Bar slip
I am trying to model reinforcement bar slip at the interface of the beam, column (Beam end or column end) with the help of fiber cross-section where the uniaxial material strains are modified. As suggested in the literature, this fiber cross-section will be assumed to be present at either end of the beam/column within a zero-length.

Flexural response
To capture the flexural response of beam/column, I have considered a force-based distributed plasticity model and there is no issue with this.

The question is how to combine the above models. Images are also attached for better representation. The STKO model file is also attached, where material properties and Fiber cross-sections are separately considered for bar slipcases and named as follows.
Material Properties
Concrete-BS
Steel-BS
Fiber sections
Ca-1-BS
Ba-1-BS
Ba-2-BS

I request you to kindly go through this and give a reply.
Attachments
BS.zip
(646.64 KiB) Downloaded 12 times

STKO Team
Posts: 893
Joined: Tue Oct 29, 2019 8:45 am

Re: Defining a Zero length Fiber cross section -

Post by STKO Team » Tue Dec 28, 2021 9:39 am

Using a zero length for the bar slip can give you some issues, as a zero-length should represent a moment-rotation, not a moment-curvature behavior. So the materials that you use in a fiber section for a zero-length, should be a stress-displacement relationship, not a stress-strain one.

I think it's easier if you use the standard force-based element, using the Hinge Radau Integration scheme.
You should pay attention to the plastic-hinge length that now should be the bar-slip effective length:
barslip.png
barslip.png (25.99 KiB) Viewed 52 times

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