Model for Response of Concrete to Random Compressive Loads

A model to predict the stress‐strain behavior of concrete composites under random cyclic compressive loadings is developed. The model uses the envelope unloading strain as an index of load history. The plastic strain and reloading strain are predicted as functions of the envelope unloading strain for both full and partial unloading and reloading. Expressions for the unloading and reloading curves are also given. The model is independent of the expression used for the envelope curve. Comparison with cyclic data shows good agreement. The model suggests a new way to conceptualize the behavior of concrete under cyclic loading, as the loading history index is related to an actual physical quantity. The model's strength is in its simplicity and generality. The model can be used for completely random loadings, in both the pre‐peak and post‐peak ranges. Potential uses include not only nonlinear analysis of earthquake‐resistant structures, but also prediction of energy dissipation and fatigue life.