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Applying distributed load on a 2D plane stress model

Applying distributed load on a 2D plane stress model

Applying distributed load on a 2D plane stress model


Usually, when one wants to apply a distributed load to a 2D plane stress model of a simply supported beam, for example, we have, in theory, to calculate the load contributions in every node of the finite elements (nodal forces). This is what I learned in my courses in college, anyway.
This is obviously very time consuming and, unless I don't entirely understand all the options SAP2000 offers to apply loads to areas, I don't see any way around it.
That is unless the method I've been using to avoid this problem is actually valid.
It's on this method's validity I want to hear some feedback on.

What I usually do is to define a soft frame (low modulus of elasticity) on the top of the 2D beam and apply my load to that frame. I also divide the frame at the intersections with the finite elements' nodes. So, is this valid or not? The tests I performed seem to show it is, but I may be missing something.

Hopefully, the following image will illustrate what I'm saying:

The load is applied in the frame (coloured yellow)

Thanks for the help

Edit: when I add the frame I always make sure to set its weight and inertia to 0

RE: Applying distributed load on a 2D plane stress model

Hi Filipe,

This is also the method we use in such situations.

Just my advice: Instead of using a "soft frame", assign the "None" section to the frame.
It is a dummy section, implemented by default into SAP, which serves for this kind of task. It just disappear during the calculation, after transferring all its loads to the elements it is attached to.
This way you do not need to worry about masses, weights, inertias, etc. you have to assign to the section.

By the way, you also have a "None" section for areas, just in case you need them. For example, it is a way of easily introducing wind loads and automatically transferring them to the columns, purlins, etc.

RE: Applying distributed load on a 2D plane stress model

That's perfect! Thank you very much for the reply and the additional tips!

Best regards,

RE: Applying distributed load on a 2D plane stress model

Make sure to put your dummy frame in the middle of the 2d plane beam, not to cause any force displacements to the origin of the beam itself.

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