Seismic analysis of masonry buildings: equivalent frame approach with fiber beam elements

The seismic analysis of masonry buildings by means of the equivalent frame simplified methodology has received considerable attention in the last decades; the walls are modeled with macroelements to represent the in-plane non-linear behavior of the panels. The mechanical characterization of these macroelements is the crucial point that defines the specific frame approach. In the present paper, the spandrels and the piers of the masonry wall are modeled through fiber section force-based elements that accounts for both axial-flexural and shear deformations, while the connecting nodes are assumed as rigid. The approach is investigated using the open source computational platform OpenSees that allows coupling between flexural and shear responses through a section aggregator procedure. The interaction between axial load and bending behavior is automatically accounted for by the fiber section model. The shear response is given by a phenomenological law and flexure - shear coupling is enforced at the element level. The approach is very simple and quite promising for both research and practice and the first numerical tests on sample cases show both numerical robustness in monotonic and cyclic analyses under vertical and horizontal loads and a satisfactory agreement with available experimental test results.