Seismic Behaviour of Thin-Bed Layered Unreinforced Clay Masonry Frames with T- or L-Shaped Piers

According to current standards, the use of unreinforced masonry is only recommended in regions of low to moderate seismicity as a resisting system to carry earthquake-induced horizontal forces. This requirement is however felt as rather conservative and leading to uneconomical constructive solutions, in particular for low seismic regions. Moreover, the seismic analysis of masonry structures has to be performed along two main perpendicular directions, usually neglecting the contribution of wall elements perpendicular to the seismic action. Horizontal elements (spandrel, etc.) are also commonly disregarded. In such a context, the present contribution provides an overview of experimental results obtained from shake table tests on unreinforced masonry frames carried out in the EQUALS Laboratory of Bristol University in order to assess, and possibly enhance, current design rules. The study is focused on the contribution of walls perpendicular to the seismic action and on the influence of the frame effect induced by the coupling of the walls through horizontal reinforced concrete elements, such as lintels and floor slabs. Another point of interest of the study is the influence of the gravity loading situation, comparing a floor slab supported by the shear walls as well as by the perpendicular elements, with a floor slab supported by the perpendicular walls only. Tests are performed on walls constructed with units and construction methods typical of the North-Western European region.