The understanding of the mechanical behavior of engineering materials and their interfaces plays an important role in the prediction, analysis, and desing of engineering systems. Considering the important role of understanding and describing the behavior of materials and systems, this thesis is devided into three sections: 1) Modeling the behavior of polymer concrete under uniaxial compression, 2) Modeling the behavior of various light- and normal- weight concretes under uniaxial and triaxial compression, and 3) Modeling the behaivor of interfaces between polymer concrete and normal concrete with sand. In this context, various constitutive models were investigated and compared together,...