Stiffness of unreinforced masonry walls subjected to static-cyclic shear

One of the most challenging and still not satisfactorily solved issues in the design of structural masonry is the determination of the stiffness of the shear walls. Determining the correct stiffness is of the utmost importance, for example for the deformation-based design of masonry structures. Even more important is capturing the degradation of the stiffness due to cyclic loading. An assessment of such degradation has been made, based on the results obtained from the full-scale testing of unreinforced masonry walls subjected to in-plane static-cyclic loading. The present paper discusses the experimental results obtained and presents a relationship capable of describing the abovementioned degradation as a function of the applied (cyclic) horizontal displacement of the top edge of the wall. Further, it addresses the question of the influence of different parameters on the shear stiffness of unreinforced masonry walls and its degradation.