Fiber elements.

[Allaaldeen]

Hi
I noticed when a lateral load is applied to a reinforced concrete fiber element (column element), the element undergoes upwards displacement. This happens with or without axial load. Furthermore, when the same element is assigned linear elastic (or steel) properties there will be no upwards displacement.
The difference between reinforced concrete section and other sections is the strain profile of the section, in case of reinforced concrete sections, the neutral axis is far from the section center, toward the compassion zone, with most of the section appears to be in tension. Whereas in the other sections the neutral axis is located near the section center.
I think the issue of upwards deflection comes from the strain profile of the sections.
I know how the lateral displacement is calculated from section curvatures. But how the axial displacement is calculated from curvatures?. Would you please recommend a reference?

[EricsonEncinaZ]

You can get the elongation of the analytical element by calculating the summation of $length_of_the_integration_point*$strain_at_midsection for each integration point that your element has.

Plastic hinge elongation has been studied since the '70, specially in New Zealand. There is lots of research for frames, but just a few for walls.

[Allaaldeen]

Thanks for your reply.