Hi I have tried to correct this by checking all my units, including solving units, recreating commands but the concrete is still far too stiff and appears to be behaving as a linear material. The F-D curve it produces is shown below compared to experimental curves, shown above.

I have re-checked my commands and they all seem to be consistant with what is recommended in section 4.9 Microplane, help guide, and i checked everything in the command reference and it appears correct.

Any advice would be great, sure what to check next.