Quantifying the out-of-plane response of unreinforced masonry walls subjected to relative support motion

Abstract

The supports of out-of-plane loaded unreinforced masonry walls in buildings are subjected to a motion that is filtered and amplified by the building structure and, in some cases, can be significantly different from the ground motion. Moreover, because these walls span one or several storeys, their top and bottom supports are subjected to motions that differ in phase and amplitude. In state-of-the-art assessment procedures for the out-of-plane stability of masonry walls any effect of a relative support motion is neglected. The objective of this paper is to study the effect of the relative support motion on the response of out-of-plane loaded vertically-spanning unreinforced masonry walls. The acceleration capacity of the walls is investigated by means of a discrete element model representative of different wall configurations. A set of ground motions covering a wide range of peak ground acceleration and peak ground displacement is used as input to the simulations. The relative motion between the wall supports is included in the model in a systematic way: firstly, through a motion that is non-synchronous but of equal amplitude; secondly, through a motion that is synchronous but of different amplitude. The effect of the relative support motion is studied on different wall configurations where the elastic modulus of masonry, the wall height-to-thickness ratio, the wall effective thickness and the overburden at the top wall are varied. The study shows that, because of the relative support motion, the acceleration capacity of the walls can drop by 20% and, in the cases where the overburden is high, by more than 50%.

A variational rigid‐block modeling approach to nonlinear elastic and kinematic analysis of failure mechanisms in historic masonry structures subjected to lateral loads

“…The ability of UDEC to model the out‐of‐plane rocking behavior of masonry structures is demonstrated in earlier works, see, for instance, Refs. 26, 28, and 70. In this study, UDEC was used to create a numerical mock‐up of the panels with the same geometry and material properties as those used in the rigid block model.…”

“…Those generally comprise analytical models, [14][15][16][17] homogeneous and discontinuous finite element models, [18][19][20][21] macroelement models, [22][23][24] as well as applied, distinct element and nonsmooth contact dynamics models. [25][26][27][28][29][30][31][32][33] Multistep models and CAD tools based on macromodeling approaches have been also proposed. 5,34 Among these methods, discontinuous modeling approaches appear to be particularly suitable for the analysis of the local collapse mechanisms, mainly thanks to the discretization and formulations adopted, which allow the activation and evolution of the mechanisms to be followed closely and without a-priori assumptions, making them adapted to the assessment methods included in the standards.…”

“…In this context, various modeling approaches have been proposed in the literature, which can be conveniently used for the analysis of local failure mechanisms. Those generally comprise analytical models, 14–17 homogeneous and discontinuous finite element models, 18–21 macroelement models, 22–24 as well as applied, distinct element and nonsmooth contact dynamics models 25–33 . Multistep models and CAD tools based on macromodeling approaches have been also proposed 5,34 .…”

Seismic rocking simulation of unreinforced masonry parapets and façades using the discrete element method

“…The earthquake response of elevated façades and parapets is significantly influenced by the principal dynamic response of the building that they are connected to. For example, for the same earthquake and at the same location, the seismic input to a parapet located at the top of a multistorey building will be different to the seismic input for the same free‐standing wall supported directly on the ground 26–28 . Recognizing the role of building amplification, in the reported study the difference between parapets and façades was studied subjected to application of the same (non‐amplified) ground motion without the building filtering the signal.…”

“…For example, for the same earthquake and at the same location, the seismic input to a parapet located at the top of a multistorey building will be different to the seismic input for the same free-standing wall supported directly on the ground. [26][27][28] Recognizing the role of building amplification, in the reported study the difference between parapets and façades was studied subjected to application of the same (non-amplified) ground motion without the building filtering the signal. However, the influence of the dynamic behavior of the building in the rocking capacity of the façade was taken into account.…”