Explicit formulation for three-dimensional cyclic analysis of R.C. structures

Scope of this work is the definition of a material law able to represent the behavior of three dimensional reinforced concrete structures subjected to cyclical load histories. Resuming the hypotheses presented in literature, as in the publications of Vecchio, who considers a orthotropic material law in both phases of loading and unloading, it has been formulated and implemented a constitutive model suitable to analysis based on explicit algorithms. The consideration of orthotropic tensional field during loading, unloading and reloading, places remarkable problems, both from theoretical and numerical points of view, because during the load history, it varies the value of the damage along a principal direction and also the principal orientation. Being the law formulated based on CFT and MCFT models class, the total answer is calculated in function of the uniaxial law, that is thought valid along each of the three principal directions. In this way, fundamental importance assumes the single uniaxial law and, of course, also the laws that govern the load and the unload of the material in three dimensional space. In order to validate the material formulation, it has been analyzed one reinforced concrete wall loaded to remarkable cyclical shear tension.