Finite element modeling incorporating non-linearity of material behavior based on the fib Model Code 2010

Non linearity is a prominent characteristic of most cement-based material. This nonlinear behavior is observed even at very low loading levels. When strain softening is present, the increase in loading will result in a decrease of structural stiffness.Most existing programs, including SAP 2000, takes into account geometric nonlinearity, but assumes a constant stiffness modulus throughout the loading process. This will result in a less accurate outcome, and can further significantly influence analysis of the overall behavior of the structure.A Finite Element Program written in the Visual Basic programming language was developed to take into account nonlinear behavior of the modulus of elasticity and the Poisson Ratio, as a function of increasing principal stresses. The results of this program were validated by laboratory tested specimens to compare the load-deformation response and accuracy of the model. The Federal Institute of Technology, Europe Model Code 2011 was used to model the material behavior and failure criterion.