A simple question about layer straight command?

[rcsoul]

The file in the example manual Ex9e.build.RCSection.Rect2D.tcl used the following script to define a fiber section. What my question is wouldn't the layer straight command defined two coincident rebars in one single point? For example, the point (-$coreY $coreZ) appeared twice in the following script. Would two steel fiber be defined in one same single point (-$coreY $coreZ)?


section fiberSec $SecTag {; # Define the fiber section
patch quadr $IDconcCore $nfZ $nfY -$coreY $coreZ -$coreY -$coreZ $coreY -$coreZ $coreY $coreZ; # Define the core patch
patch quadr $IDconcCover 1 $nfY -$coverY $coverZ -$coreY $coreZ $coreY $coreZ $coverY $coverZ; # Define the four cover patches
patch quadr $IDconcCover 1 $nfY -$coreY -$coreZ -$coverY -$coverZ $coverY -$coverZ $coreY -$coreZ
patch quadr $IDconcCover $nfZ 1 -$coverY $coverZ -$coverY -$coverZ -$coreY -$coreZ -$coreY $coreZ
patch quadr $IDconcCover $nfZ 1 $coreY $coreZ $coreY -$coreZ $coverY -$coverZ $coverY $coverZ
layer straight $IDreinf $numBarsInt $barAreaInt -$coreY $coreZ $coreY $coreZ; # intermediate skin reinf. +z
layer straight $IDreinf $numBarsInt $barAreaInt -$coreY -$coreZ $coreY -$coreZ; # intermediate skin reinf. -z
layer straight $IDreinf $numBarsTop $barAreaTop $coreY $coreZ $coreY -$coreZ; # top layer reinfocement
layer straight $IDreinf $numBarsBot $barAreaBot -$coreY $coreZ -$coreY -$coreZ; # bottom layer reinforcement
}; # end of fibersection definition

[fmk]

if a start point or end point is defined twice in the layer command it will result in 2 fibers.

[andreascj]

Vesna,

I have same confusion as this very old post.

Thanks.

[vesna]

What are you confused about?

[andreascj]

With the script shown by rcsoul above (also given in OpenSees examples), there will be two steel fibers at the same location in the section. This will be inaccurate. Vesna, could you please clarify, how the script given in OpenSees examples is in fact correct? I know that "layer" command can be used to create fibers in whatever way we like but I am concerned about the scripts given in OpenSees examples.

Thanks.

[vesna]

I do not know if Silvia intentionally had two fibers at the same location or if that was a mistake.

If you do not want two fibers at the same location you just need to have start and end points of one layer at different locations from all other layers.

You should not follow the examples blindly. It is important to understand all the commands within the model, understand procedures, and learn OpenSees from those.

[andreascj]

Thanks Vesna,

In that case, shouldn't the example file be modified? Why would we have two steel fibers at the same location, even for an example?

[andreascj]

Hi Vesna,

One related question. What happens if we define a straight layer with only one fiber? Does that fiber become located at the center of the layer, or beginning/end?

Thanks.

[vesna]

I would not use "straight layer" for one fiber only. I would rather use "fiber" option.

I believe that the minimum number of fibers that can be specified with the "straight layer" is 2.

[Ganeshram]

I also encounter this confusion in OpenSees Examples given in OpenSees website. The reinforcements coincide not only in a single fiber but the four corner of the section in the given examples. Would you some one explain please? Thank you.