Displacement capacity of masonry structures under horizontal actions via PRD method

The displacement capacity of masonry structures, investigated through the piecewise rigid displacement (PRD) method, is the principal focus of the present study. Since a masonry construction exhibits a rigid block mechanism when shaken by severe earthquakes, by adopting the Heyman material restrictions, the PRD method can be used to look for the global collapse mechanism of the structure under horizontal actions and the static load multiplier. As a result of this investigation, a one-degree of freedom mechanism is detected. In the moving part of the collapsing structure, the field of relative displacement among the blocks allows to identify the fracture distribution. The paper examines the stability of masonry constructions analysing the displacement capacity curves which is obtained by a kinematical incremental analysis via PRD method, operating in the framework of limit analysis. The displacement capacity of the structure is defined as the maximum displacement in which the potential energy assumes a local maximum. Consequently, the moving part of the structure in this configuration is unstable. Finally, two examples are exposed in detail to show the performance of the PRD method.