The Mandela Effect refers to a belief that is widely held, but completely false. Examples, some of which are admittedly a stretch, range from common misspellings to frequently misquoted movie lines.
The Mandela Effect applies to OpenSees as well.
Along the lines of misspellings, there is a widely held belief that OpenSees is capitalized OpenSEES. No CAPS!
Another widely held–but false–belief is that only one “fiber element” is available in OpenSees. There are actually several elements that can use fiber sections, so be more specific!
But the ultimate widely held falsehood is that the static resisting force in a nonlinear analysis is the matrix-vector product of tangent stiffness with nodal displacements. When I see the equation of motion has 
Can you think of other examples of the Mandela Effect related to OpenSees? Share your examples in the Comments section below.
Portwood Digital 
I think another common one is writing the equation of motion for a nonlinear system including only the ground motion load -Mlu_ddot on the right-hand side but forgetting the gravity loads. As if LoadConst was removing the gravity loads from the equation.
LikeLiked by 1 person
Ha, that is a good one! I’m certain I’ve made that mistake before 🙂
LikeLiked by 1 person
Same 🙂
LikeLike