Trapezoidal Load on Beam Element

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ankurjain1992
Posts: 41
Joined: Mon Aug 03, 2020 5:38 pm

Trapezoidal Load on Beam Element

Post by ankurjain1992 » Mon Aug 10, 2020 5:58 pm

Sir, How can I apply Trapizoidal/Triangular load in STKO Opensees. I am able to find the option for applying Uniformly Distributed Load but unable to find for the Trapezoidal Load and Triangular Load. Kindly help.
Attachments
load.png
load.png (62.86 KiB) Viewed 710 times

STKO Team
Posts: 434
Joined: Tue Oct 29, 2019 8:45 am

Re: Trapezoidal Load on Beam Element

Post by STKO Team » Mon Aug 17, 2020 9:04 am

Unfortunately OpenSees does not have a triangular or trapezoidal eleLoad (that is, a load distributed in closed form over a single finite element).

However this can be done in STKO using the load->EdgeForce, using the option Mode=function. In this way you can define a custom Python function (of x, y, and z global coordinates).
Keep in mind, however, that in this way you can define any kind of function (triangular, trapezoidal or whatever... ) but since there is no equivalent eleLoad, STKO will convert this distributed EdgeForce into a set of equivalent (lumped) nodal loads.
This means that you need to discretize the beam/column with more that 1 finite element.
custom_load.png
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ankurjain1992
Posts: 41
Joined: Mon Aug 03, 2020 5:38 pm

Re: Trapezoidal Load on Beam Element

Post by ankurjain1992 » Mon Aug 17, 2020 6:33 pm

Thank you so much STKO Team ...

If possible kindly attach the file that you made because I have done the same in STKO as you said but I am not able to see any loads in the Opensees TCL files after I write them.

STKO Team
Posts: 434
Joined: Tue Oct 29, 2019 8:45 am

Re: Trapezoidal Load on Beam Element

Post by STKO Team » Tue Aug 18, 2020 9:29 am

Here is a sample file with the same triangular load (EdgeForce) applied to 4 beams.
Each beam has been subdivided (meshed) into a different number of elements.
In cases such as this one, i.e. a custom distributed load that is not available in OpenSees, you can still use this feature in STKO, but STKO will convert that load to a set of equivalent (lumped) nodal loads. Now, since they are nodal loads, you need to discretize your element to see internal deformations.

Here is the file:
customload.zip
(99.38 KiB) Downloaded 28 times

And here is an example of how to mesh edges with different numbers of subdivision (use the EdgeSeed command)
Here I used 1, 2, 4, and 8 subdivisions, of course the best result is obtained with the beam with more subdivisions:
custom_load_mesh.png
custom_load_mesh.png (103.66 KiB) Viewed 679 times

These are the equivalent nodal loads written in TCL:
custom_load_equivalent_loads.png
custom_load_equivalent_loads.png (53.24 KiB) Viewed 679 times

ankurjain1992
Posts: 41
Joined: Mon Aug 03, 2020 5:38 pm

Re: Trapezoidal Load on Beam Element

Post by ankurjain1992 » Tue Aug 18, 2020 12:14 pm

Great work sir ....Thank you so much

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