Non-buckling element

[alima2065]

Hi everyone,
Which frame(wire) element can not buckle in Abaqus implicit. Is truss like that?
Thank you in advance.
Regards,
Ali

 

[SWComposites]

an element loaded only in tension. things loaded in compression tend to buckle under sufficient load.

 

[FEA way]

A single truss element shouldn't buckle but you could use spring or connector elements if you want to be sure.

 

[alima2065]

Thank you for your reply. A single truss element doesn't buckle. However, I need to change the section at the end, and I need to use 3 of them.
Regarding axial connectors, I found that the section stiffness parameter(AE) is defined and Abaqus calculates the member stiffness (AE/L) based on the wire length. Is it right?

 

[FEA way]

Even multiple truss elements used to model a single member normally shouldn't buckle, if that's what you mean. Still, I would advise connector elements. The axial connector has a very simple formulation (described in the documentation chapter: Elements --> Connector Elements --> Connector Elements --> Connection Types --> Connection-Type Library --> AXIAL) and you just have to specify its stiffness D (in F/L units).

 

[alima2065]

I am not sure if we can call it buckling, but when I used multiple truss elements (bottom brace in the figure), I had a deformed brace similar to buckling. When I used a single element, the deformed shape seemed okay, but I could not change the property of the section by the length. I checked both implicit and explicit, and the same behavior was observed.

 

[FEA way]

Why don't you use beam elements for this purpose ? Of course, they can buckle but in a realistic way so only when a member would buckle in real life.

To check if the observed buckling makes sense, you can run a linear buckling analysis.

 

[alima2065]

The aim of this is to model a buckling restrained brace (BRB). They don't buckle and yield both in tension and compression. Another point is that they are assumed to be pinned at two ends. The beam element can apply bending moments on the structure (beams and columns).

 

[FEA way]

Then it seems that connector elements will be the best for this. You can even include plasticity in their behavior.