Force Recorder Sign Convention

[bjturner]

Can somebody explain the sign convention used when the recorder generates an output file for element forces? I realize that it's in terms of global coordinates, but I'm not altering the global coordinate system between the two nodes which define my element and yet I'm getting opposite signs for, e.g., shear forces.

Also, is the order of the output defined by how you define the degrees of freedom, or is it always in a certain order, or something else? I'm unable to find a description of this in the command library, if somebody could point me in the right direction it would be much appreciated.

Thanks,
Ben

[chayton]

i think a simple canti-Column example will definitely helps you out!

[kostast88]

Element recorder can record:
force || globalforce = global forces with the sign convention : y positive upwards,x positive to the right
localforce = local forces (where shear force is axial for columns eg)

If something is not right,perhaps you should check your input,external forces sign.External forces are always defined in global coordinates.

[chayton]

kostast88 wrote:
> Element recorder can record:
> force || globalforce = global forces with the sign convention : y
> positive upwards,x positive to the right
> localforce = local forces (where shear force is axial for columns eg)
>
>
> If something is not right,perhaps you should check your input,external
> forces sign.External forces are always defined in global coordinates.
Add:the force record convention has someting to do with the sequence of connecting nodes.

[vesna]

The force recorder outputs the forces such that the sign convention and the order corresponds to the sign and order of global coordinate axes. It first outputs forces at node i and then at node j. The force aligned with the global X axis will be output first. It is followed by the forces in global Y and Z directions and then by moments in X, Y, and Z directions.

For the column subjected to lateral load, forces perpendicular to the element (that produce shear force for the element) should have opposite signs at the element ends.