Influence of boundary conditions on the out-of-plane response of brick masonry walls in buildings with RC slabs
In modern unreinforced masonry buildings with stiff RC slabs, walls of the top ﬂoor are most susceptible to out-of-plane failure. The out-of-plane response depends not only on the acceleration demand and wall geom-etry but also on the static and kinematic boundary conditions of the walls. This paper discusses the inﬂuence of these boundary conditions on the out-of-plane response through evaluation of shake table test results and numerical modelling. As a novum, it shows that the in-plane response of ﬂanking elements, which are or-thogonal to the wall whose out-of-plane response is studied, has a signiﬁcant inﬂuence on the vertical re-straint at the top of the walls. The most critical conﬁguration exists if the ﬂanking elements are unreinforced masonry walls that rock. In this case, the ﬂoor slabs can uplift, and the out-of-plane load-bearing walls loose the vertical restraint at the top. Numerical modelling conﬁrms this experimentally observed behaviour and shows that slab uplift and the difference in base and top excitation have a strong inﬂuence on the out-of-plane response of the walls analysed.