The nonlinear analysis model for reinforced concrete plane frame structures is based
on the simplified concept of the localization of irreversible physical processes at
previously definite zones, denominated here as generalized hinges. However, when
both damage due to the microcracking of concrete and sliding mechanisms
(aggregate interlocking) at crack surfaces are taken into consideration, hysteresis
loops can be reproduced if the loading history includes unloading cycles. The
thermodynamic approach of the model is herein developed with reference to
generalized variables due to its application in the framework of the classical
theory of bars under bending load. According to this model, there are three
scalar variables: a damage variable, the plastic rotation of the section and the
sliding-associated rotation of the section. By comparison with available experimental
responses, the numerical examples illustrate the good performance of the
model.
