Non linear analysis of mixed masonry and reinforced concrete buildings

From the early 20th-century the gradual transformation of the theory and constructive techniques led from the masonry buildings predominance to the reinforced concrete’s (RC) structures. Together with structures conceived with a definite role for the earthquake behaviour, the spreading of RC technology caused the birth of mixed solutions starting from existing structures in order to satisfy functional aspects: masonry structures subjected to internal demolishment, column insertions, RC staircases insertions, plan enlargements or raisings-up by mean of concrete structures. The structural variety is quite wide and the complex set of specific cases eludes the coded schemes: therefore subject of particular interest becomes the vulnerability of this class. Moreover, although there is a well-established background focused on the non linear analysis of masonry structures and RC frames, the set of numerical and experimental instruments for the study of the interaction effects is limited. In this paper, in the masonry’s idealisation as equivalent 3D frame (Galasco et al., 2004), a formulation and implementation of non linear elements is proposed in order to model RC columns, beams and walls. The adopted approach idealises the behaviour as elasto-perfectly plastic with limited resistance and plasticity concentrated at the end-element; the considered failure’s mechanisms are as follows: shear and axial stress as brittle failure and axial-bending as ductile failure. Some examples show the efficiency of this method and highlight the behaviour’s peculiarity of these structures.