Abstract
Researchers and practitioners widely employ simplified Equivalent Frame Models (EFM) for reproducing the in-plane governed response of unreinforced brick masonry (URM) structures, as they typically represent an acceptable compromise between numerical accuracy and computational cost. However, when considering URM structural systems with irregular opening distribution, the definition of the effective height and length of deformable components (i.e. pier and spandrel elements) still represents an open challenge. In this work, the influence of irregular distribution of openings on the predicted lateral response of full-scale URM façades was investigated. To this end, several geometrical combinations characterised by various degrees of irregularity were considered and idealised according to commonly employed EF discretisation approaches. Then, after a preliminary calibration process against experimental tests on both individual piers and a full-scale building façade, EFM results were compared with micro-modelling predictions, carried out within the framework of the Applied Element Method and used as a benchmark. Although in specific irregular configurations using some discretisation approaches, macro and micro-models converge to similar results, non-negligible differences in terms of initial lateral stiffness, base-shear and damage distribution were observed with other EF schemes or opening layouts, thus indicating that a careful selection of appropriate criteria is indeed needed when performing in-plane analyses of URM systems with irregular opening distributions. Finally, building on inferred simulated data, potential solutions are given to overcome typical EF discretisation issues and better approximate micro-modelling outcomes.
Highlights
To simulate the in-plane (IP) behaviour of unreinforced masonry (URM) structures under seismic loading, several different modelling methods are presently available in the literature, ranging from advanced micro-modelling to the more simplified macro-modelling approaches (Lourenço 2002; Roca et al 2010; D’Altri et al 2020)
Equivalent Frame Models are widely employed in the seismic assessment of the in-plane governed behaviour of unreinforced masonry buildings, representing a good compromise between accuracy and computational burden when performing large-scale nonlinear analyses
LIM and average, AVG, effective height criteria), based on simple geometrical rules, were selected. Their effectiveness was analysed in a study investigating the differences in terms of predicted in-plane behaviour of multiple opening configurations derived from a baseline model, i.e. an experimentally tested building façade
Summary
To simulate the in-plane (IP) behaviour of unreinforced masonry (URM) structures under seismic loading, several different modelling methods are presently available in the literature, ranging from advanced micro-modelling to the more simplified macro-modelling approaches (Lourenço 2002; Roca et al 2010; D’Altri et al 2020). A low degree of idealisation typically characterises micro-modelling approaches (D’Altri et al 2020), according to which the actual masonry texture is explicitly reproduced, unit-by-unit In this framework, discrete models, initially conceived to analyse soil mechanics problems, proved to be suitable for simulating IP-governed responses of URM components and building sub-systems (Malomo et al 2019a, Pulatsu et al 2020). In the AEM, masonry members are represented as an assembly of rigid elements connected by nonlinear springs interfaces, where material properties are lumped and failure occurs This efficient tool proved to be suitable to model the heterogeneous nature of URM structures, enabling the possibility of representing their behaviour up to complete collapse (Karbassi and Nollet 2013; Keys and Clubley 2017; Malomo et al 2020)
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