In code recommendations, the drift capacity of unreinforced masonry (URM) walls is often estimated as a function of the failure mode and the aspect ratio. The empirical relationships are based on results from quasi-static cyclic tests on single URM walls, which were tested simulating either fixed-fixed or cantilever boundary conditions. In real structures, the stiffness and strength of slabs and spandrels define the boundary conditions of the piers and, therefore the moment, shear force and axial force imposed on a pier during an earthquake. Depending on the exact configuration of wall, slab and spandrel, the boundary conditions can vary significantly.
In order to investigate the influence of these boundary conditions on the force-deformation behaviour of URM walls, we tested six identical URM walls (PUP). The test units were subjected to quasi-static cycles of increasing drift demands and the tests differed with regard to the applied axial load and the moment restraint applied at the top of the walls. Throughout the loading, the deformations of the piers were recorded using an optical measurement system tracking the movement of 312 LEDs per test unit (4 LEDs per brick). Previous test data on URM walls focused on the global response of the wall. Thus, this new dataset allows us to link global to local deformations.
Scaling of unreinforced masonry
When testing multi-storey structures, most testing facilities require the testing of a reduced-scale model. Previous tests of scaled masonry structural components revealed that scaling of masonry is rather challenging and often significant differences in stiffness, strength and failure mechanisms between the different sized masonry are reported. This research addresses the scaling of hollow clay brick masonry with fully mortared head and bed joints. We investigated different choices of reduced-size brick units and mortar joints. Based on the results of an extensive test programme including standard material tests and quasi-static cyclic tests on masonry walls, we formulate recommendations for the production of a half-scale model of unreinforced masonry structures. The experimental results show a good match between full-scale and half-scale masonry. The half-size brick was used for the construction of a 4-storey building, which was tested dynamically (CoMa-WallS project).
Influence of boundary conditions and size effect on the drift capacity of URM walls [journal link]
- Cyclic test data of six unreinforced masonry walls with different boundary conditions [journal link]
- Scaling unreinforced masonry for reduced-scale seismic testing [journal link]
- Limit states of modern unreinforced clay brick masonry walls subjected to in-plane loading [journal link]
- Funding: Morandi Frères SA (in-kind contributions)