Chang-Mander nonlinear concrete model - con_cm

It is the implementation of Chang & Mander's [Chang & Mander, 1994] concrete model, which puts particular emphasis on the transition of the stress-strain relation upon crack opening and closure, contrary to other similar models that assume sudden crack closure with rapid change in section modulus. The concrete in tension is modeled with a cyclic behaviour similar to that in compression, and the model envelopes for compression and tension have control on the slope of the stress-strain behaviour at the origin, and the shape of both the ascending and descending (i.e. pre-peak and post-peak) branches of the stress-strain behaviour.

Users have to assign the mean value of concrete strength and the mean value minus the standard deviation or the characteristic value in order to describe the mechanical characteristics of the existing or the new material respectively.