Trapezoidal Load on Beam Element

[ankurjain1992]

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.

[STKO Team]

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 (125.4 KiB) Viewed 695 times

[ankurjain1992]

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]

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 (103.66 KiB) Viewed 680 times

These are the equivalent nodal loads written in TCL:

custom_load_equivalent_loads.png (53.24 KiB) Viewed 680 times

[ankurjain1992]

Great work sir ....Thank you so much