A methodological framework to relate the earthquake-induced frequency reduction to structural damage in masonry buildings

Brunelli

2023

Bull Earthquake Eng

Self Cite

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.

Section: Shear Behaviourmentioning

confidence: 99%

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

Brunelli

2023

Bull Earthquake Eng

Self Cite

“…This can be useful not only to validate numerical models but also to assign a synthetic DL value to the huge amount of data from a time-history with the aim of deriving fragility curves or tools useful to support the decision-making process in the post-earthquake scenario. While in this paper only the first goal is exemplified, examples of the second ones are provided in Brunelli et al (2022) and (Sivori et al 2022), respectively. The numerical models of the case studies presented in Sect.…”

Section: Potential Of the Proposed Procedures For Validating Numerica...mentioning

confidence: 99%

Multiscale procedure to assign structural damage levels in masonry buildings from observed or numerically simulated seismic performance

2022

Bull Earthquake Eng

Self Cite

The damage level (DL) is a fundamental metric in earthquake engineering and is particularly effective for multiple purposes, such as correlating structural damage to consequences and losses (e.g. economic, casualties, etc.) as well as to physical and mechanical variables quantifiable from both experimental and numerical tests. Despite the relevance of the topic, the conversion of complex information on the damage spreading over a 3D building into a synthetic DL remains an open issue for which there are currently no agreed-upon scientific criteria in the literature. Within this context, the study focuses on unreinforced masonry (URM) buildings by providing an analytical multi-scale approach that integrates structural damage at the panel-scale and macro-element size (where the macro-element is intended as an assemblage of components, like vertical walls or diaphragms). The approach is specifically conceived to be applied consistently to both observed and numerically simulated damage. As a result, the method is particularly effective for supporting the validation of numerical models or synthetically interpreting the huge amount of results from nonlinear analyses as much as feasible using an objective basis. The paper proposes a comparison of DL interpretation arising from other approaches in the current literature, highlighting their pros and cons. The effectiveness of the proposed procedure is then assessed using four URM case studies, all of which exhibited primarily a ‘box-like behaviour’. They were specifically chosen based on the extremely detailed documentation available for both the damage and geometric/mechanical features of the buildings as well as aiming to reduce the uncertainty in the seismic input, making them ideal candidates also for validation purposes. To this end, the applicability of the procedure also to the damage simulated by nonlinear dynamic analyses was proven by adopting equivalent frame models of the case studies, developed and calibrated in previous researches. Definitely, the results encourage the adoption of the proposed procedure to interpret as analytically as possible the real damage that occurred on URM building, when accurate damage observations from field surveys are available, as well as that coming from numerical simulations.

“…In particular, the multiscale approach originally proposed in (Lagomarsino and Cattari 2015) and then further developed in (Sivori et al 2022, Brunelli et al 2022b) was adopted to assign a speci c damage level to the building compatible with the EMS98 scale (i.e. from DL1 to DL5).…”

Section: Global In-plane Responsementioning

confidence: 99%

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

Brunelli

2022

Preprint

Masonry buildings in aggregate are largely diffused within the existing Italian and European building stock, especially in historical centres. Their seismic evaluation 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 masonry aggregate. The latter consists of five adjacent structural units mutually interacting with each other during seismic sequences. The aggregate is inspired by the unreinforced masonry (URM) built heritage of the historic centre of Visso struck by the Central Italy 2016/2017 earthquakes. It was proved to be negatively affected especially by the site-amplification phenomena. 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. Also an innovative procedure considering the pounding effect to the global response of the building was presented. Two soil conditions were assumed with (freefield) and without (bedrock case) site amplification. In the first case, a site response analysis based on a 1D soil model aimed to reproduce the actual soil profile under the examined aggregate has been carried out. The results showed that site effects strongly affected the seismic vulnerability of the aggregate, also possibly altering the combination between IP and OOP mechanisms with respect to what expected on basis of evidence from other historical centres. More specifically, for bedrock condition, the overall seismic response of the buildings in aggregate was strongly affected by such a combination, especially for medium-high damage levels where 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. The result appears also affected by the architectural configuration of such buildings, characterized by quite large openings at ground floor.