Fragility curves of masonry buildings in aggregate accounting for local mechanisms and site effects

Abstract

The seismic evaluation of masonry buildings in aggregate, largely diffused within the existing Italian and European building stock, represents a difficult and open task that has not been exhaustively investigated so far. The study proposes a procedure aimed at evaluating the potential impact of the combination of local mechanisms and site-amplification in terms of fragility curves on an existing unreinforced masonry (URM) aggregate which is made of five adjacent structural units mutually interacting with each other during seismic sequences. The case study is inspired by built heritage of the historic centre of Visso struck by the Central Italy 2016/2017 earthquakes. The in-plane (IP) response of URM buildings was simulated through nonlinear dynamic analyses performed on a 3D equivalent frame model of the structure, whereas out-of-plane (OOP) mechanisms were analysed by adopting the rigid-block assumption but assuming, as seismic input, the floor accelerations derived from the post-processing of data derived from the global 3D model. An innovative procedure considering the pounding effect to the global response of the building is also presented. Two soil conditions were assumed with (freefield) and without (bedrock) site amplification. The results showed that site effects strongly affected the seismic vulnerability of the aggregate, also altering the combination between IP and OOP mechanisms. In fact, for bedrock condition, especially for medium–high damage levels, local mechanisms were prevailing with respect to the IP response. Conversely, for freefield condition, IP mainly governed the overall behaviour for all the damage levels, consistently with the field evidence.

Empirical Fragility Analysis of Haitian Reinforced Concrete and Masonry Buildings

“…These models simulate the behavior of structures under seismic loads to predict damage outcomes. The analytical approach is extensively utilized in deriving fragility curves, encompassing several key steps [24][25][26][27]: (i) developing Finite Element (FE) models for the specific building types under investigation; (ii) selecting a comprehensive suite of ground motions to accurately simulate earthquake-induced shaking; and (iii) performing non-linear time-history analysis. This analysis aims to establish a correlation between the chosen earthquake intensity measure (IM) and the engineering demand parameter, which is typically represented by the maximum interstory drift.…”

Seismic Fragility Evaluation of Typological Masonry Aggregates Accounting for Local Collapse Mechanisms

“…Angiolilli et al [24] derived fragility curves for a masonry aggregate having an L-shape, by focusing on the corner structural unit and by analysing the possible differences with different connection types among the buildings. Still, Angiolilli et al [25] proposed a procedure to investigate pounding effect among buildings composing a masonry aggregates, accounting for different soil conditions and in-plane and out-of-plane effects.…”

Damage Evaluation and Seismic Assessment of a Typical Historical Unreinforced Masonry Building in the Zagreb 2020 Earthquake: A Case Study—Part I

“…A newly developed microelement for a frame element modeling approach that accounts for both in-plane and out-of-plane failure modes is used in research study [26] for modeling historical masonry buildings with timber floors, and it is highlighted that modeling the out-of-plane behavior has a significant impact on the seismic fragility curves. Furthermore, fragility curves for typical URM buildings with the out-of-plane effect are developed and given in [27,28].…”