Macroelement Modelling Based on a Bouc – Wen Formulation with Degradation for the Dynamic Analysis of Masonry Walls

Among the different finite element modelling approaches available for the description of unreinforced masonry structures, the equivalent frame method is widely diffused. It is, in fact, capable of describing the response of masonry walls with good accuracy, thanks to the possibility of reproducing its main in-plane collapse mechanisms through the schematization of piers, spandrels and rigid zones with one-dimensional macroelements. Nonlinear hinges completed with appropriate constitutive laws are employed for the description of the nonlinear characteristics of masonry, both for shear and flexural mechanisms. In particular, a Bouc-Wen formulation is considered in this study and modified with the introduction of degradation by means of a scalar variable for damage and an additional parameter for flexibility increase, to properly account for the strength and stiffness degrade typical of masonry under cyclic actions. The dynamic behavior of a squat masonry wall under different types of excitations is investigated, as well as the effects of the damage and flexibility increase in the dynamic response of the panel.