Seismic assessment of unreinforced masonry structures: a coupled mesoscale-DMEM approach

A numerical investigation is performed to investigate the potential of a discrete macro-element coupled with a mesoscale approach for the seismic assessment of unreinforced masonry structures. At first, parametric analyses are performed on a U-shape stone masonry prototype. Nonlinear static analyses are performed to investigate parameters that affect the results when a mesoscale masonry pattern representation is adopted. Results prove the suitability of a mesoscale representation of unreinforced masonry structures through a discrete macro-element approach. Furhthermore, it is demonstrated that an irregular placement of masonry units’ have a significant role in the structural response, either from a strength and ductility standpoints, when compared to a regular and periodic distribution of units

Simulation of the Out-of-Plane Behaviour of URM Walls by Means of Discrete Macro-Element Method

The seismic response of masonry structures without box-type behaviour is given by a complex interaction between in-plane and out-of-plane behaviours. Previous earthquakes demonstrated that out-of-plane failure mechanisms represent the main cause of structural collapses of UnReinforced Masonry (URM) and historical structures. Previous experimental and analytical studies, investigating the out-of-plane behaviour of URM structures, mostly considered the effects of one-way bending moment. In this regard, recent experimental campaigns and numerical simulations have been conducted in order to investigate the out-ofplane behaviour of masonry walls subjected to two-way bending. These investigations have demonstrated the complexity of this mechanism and stressed the need for accurate numerical tools capable of providing reliable predictions in terms of ultimate strength and failure mechanisms. This paper focuses on the assessment of the dynamic behaviour of a U-shape URM prototype, subjected to shaking table tests, by means of a simplified computational strategy denoted as Discrete Macro-Element Method (DMEM). In this investigation, a comparison between experimental and numerical results was conducted in order to validate the capabilities of the proposed modelling approach. Subsequently, a parametric analysis was carried aiming at determining the influence that masonry mechanical properties, and additional model parameters, have on the out-of-plane nonlinear dynamic response of URM masonry structures

Microscopy assisted fabrication of a hydrogel-based microfluidic filter

A porous filter is fabricated directly inside a microfluidic circuit using a photoreticulable hydrogel. The filter could be used for separation of cells from blood, removal of particles or solutes, such as proteins, in microdialysis and microfiltering. The filter is realized by in situ polymerization approach: a liquid hydrogel is injected in a microfluidic circuit channel where the filter is formed in a specific location by polymerization of UV light, focused by an optical microscope

In-plane Behaviour of an Iron-Framed Masonry Façade: Comparison between Different Modelling Strategies

The ‘baraccato’ system is a construction technique with genius earthquake resilient features, used for the reconstruction of the historical city centres in the South of Italy after the catastrophic events occurred in the 18th-19th centuries. A very interesting example of such a building typology is represented by the Church of Santa Maria Maddalena, located in the municipality of Casamicciola Terme of the Ischia Island and built in 1896, after the catastrophic earthquake of 1883. The church is characterized by a mixed ‘baraccato’ system mainly made of yellow tuff block masonry walls strengthened by iron profiles or wooden elements. The reduced damage suffered by the church after the seismic event of 21st August 2017 evidenced the good behaviour of such a mixed structural system, especially into avoiding out-of-plane mechanisms. The presence of the iron-framed system is even more challenging in the definition of the modelling strategies for the structural analysis of the church. Thus, the choice of an appropriate numerical strategy to be used for nonlinear simulation should be properly investigated since the interaction between the frame elements and the elements representing the masonry walls has to be considered. As a first step of the structural analysis of the whole church, the in-plane behaviour of the main façade of the Church of Santa Maria Maddalena is analysed in this paper, with the aim to evaluate the efficacy of different modelling strategies. In particular, the study considers different models according to Finite and Discrete Element strategies available within DIANA FEA [1] and 3DMacro [2] software, respectively. Non-linear static analyses are carried out by means of both software and the obtained results are compared and discussed with the aim of extending them to the study of the whole church

A model for pushover analysis of confined masonry structures : implementation and validation

Confined masonry (CM) is a typical building technique in Latin American countries. This technique, due to its simplicity of construction and similarity with traditional practices of reinforced concrete building, presents a potential of use in European regions with moderate-to-high seismicity. However, most of the procedures for seismic design in codes for Latin America are force-based, which appears to be inadequate due to the high dissipative response observed for CM. This paper presents a simplified numerical-analytical approach to model CM structures using pushover analysis, aiming to apply performance-based design procedures. First, a data mining process is performed on a database of experimental results collected from lateral tests on CM walls to adjust prediction models for the wall shear strength and to determine the input relevance through a sensitivity analysis. Then, an analytical model of CM structures for pushover analysis is proposed with basis on a wide-column approach that employs an adaptive shear load-displacement constitutive relation. The proposed method is compared with a discrete element model that represents explicitly the confinements-masonry interaction, against the experimental results obtained in a quasi-static test of a full-scale tridimensional CM structure. The accuracy of the predictions from both methods is very satisfactory, allowing to capture the base shear-displacement envelope and also the damage patterns of the structure, thus, demonstrating the ability of the methods to be used in performance-based seismic assessment and design of CM buildings.The first author acknowledges the financial support from the Portuguese Foundation for Science and Technology (FCT) through the Ph.D. Grant SFRH/BD/41221/2007

Pain in Multiple System Atrophy a Systematic Review and Meta-Analysis

Background: Individuals with multiple system atrophy (MSA) often complain about pain, nonetheless this remains a poorly investigated non-motor feature of MSA. Objectives: Here, we aimed at assessing the prevalence, characteristics, and risk factors for pain in individuals with MSA. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guidelines, we systematically screened the PubMED, Cochrane, and Web of Science databases for papers published in English until September 30, 2022, combining the following keywords: “pain,” “multiple system atrophy,” “MSA,” “olivopontocerebellar atrophy,” “OPCA,” “striatonigral degeneration,” “SND,” “Shy Drager,” and “atypical parkinsonism.”. Results: The search identified 700 records. Sixteen studies provided information on pain prevalence in cohorts of MSA individuals and were included in a qualitative assessment based on the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Thirteen studies (11 cross-sectional, two longitudinal) scored ≥14 points on QUADAS assessment and were included in a quantitative analysis, pooling data from 1236 MSA individuals. The resulting pooled prevalence of pain in MSA was 67% (95% confidence intervals [CI] = 57%–75%), and significantly higher in individuals with MSA of parkinsonian rather than cerebellar type (76% [95% CI = 63%–87%] vs. 45% [95% CI = 33%–57%], P = 0.001). Pain assessment tools and collected information were highly heterogeneous across studies. Two studies reported pain treatment strategies and found that only every second person with MSA complaining about pain had received targeted treatment. Conclusions: We found that pain is a frequent, but still under-recognized and undertreated feature of MSA. Further research is needed to improve pain detection and treatment in MSA

Investigating the seismic response of URM walls with irregular opening layout through different modeling approaches

TThe façade and internal walls of unreinforced masonry (URM) buildings often present an irregular opening layout, due to architectural reasons or modifications to the structure, which make the expected seismic damage pattern less predictable a priori. Therefore, the discretization of the walls in structural components is not standardized, conversely to cases with a regular opening layout for which the available modeling methods are corroborated by seismic damage surveys reporting recurrent failure patterns. The structural component discretization is a relevant step for the code-conforming seismic assessment, typically based on comparing the internal forces and drifts of each component to strength criteria and drift thresholds. Therefore, the lack of well-established approaches can significantly influence the assessment. The issue is even more evident when the structural components must be identified a priori in the modeling stage, namely for equivalent frame models. The applicability of available methods for discretization of URM walls with irregular opening layout has been already investigated in literature, but a conclusive judgment requires further studies. In this context, this paper presents an overview of the preliminary results addressing the numerical modeling of this type of walls within the framework of the DPC-ReLUIS 2022-2024 project (Subtask 10.3), funded by the Italian Department of Civil Protection. The Subtask aims to propose consensus-based recommendations for researchers and practitioners which can contribute to harmonize the use of different modeling approaches. Seven research groups are involved in the research, adopting different modeling approaches and computer codes, but similar assumptions and the same analysis method (pushover) are used. The benchmark URM structure illustrated in the paper is a two-story wall from which four configurations with increasing irregularity of opening layout were derived. The results of four modeling approached are presented. Three of them reproduce the mechanical response of masonry at the material scale by means of FE models implemented in OpenSees, DIANA and Abaqus software, while the remaining approach describes the mechanical response of masonry at the macro-element scale in 3DMacro software. Results were compared in terms of capacity curves, predicted failure mechanisms and evolution of internal forces in piers. The adoption of consistent assumptions among the different approaches led to an overall agreement of predictions at both wall and pier scales, particularly in terms of damage pattern with higher concentration of damage at the ground story. Despite that, differences on the pushover curves have been highlighted. They are mainly due to some deviations of the internal forces in squat piers deriving from a complex load flow in these elements.DPC - Dipartimento della Protezione Civile, Presidenza del Consiglio dei Ministri(LA/P/0112/2020

Discrete modelling of externally bonded composite layers on masonry structures

The safeguard of existing masonry structures requires the adoption of structural retrofitting strategies able to preserve the architectural of the construction. Numerous strengthening techniques are available for the rehabilitation of exitsting structures, including historic and monumental buildings, most of them based on the application of Externally Bonded Composite (EBC) layers on the masonry surfaces. Such a technique represents a low-invasive retrofitting strategy widely used in engineering practice. In this paper, within the framework of the Discrete Macro-Element Method (DMEM) already introduced by the authors, an original macro-element for modelling the interaction between masonry elements and EBC layers is presented. The proposed model is able to provide a reliable simulation of the EBC layer applications to masonry structures although maintaining a low computational burden. After a theoretical description of the EBC macro-element, the new macro-modelling approach is validated against experimental and numerical tests available in the literature

FRP-reinforced masonry structures: Numerical modeling by means of a new discrete element approach

The protection of existing historical masonry structures represents a relevant topic in view of the high social and economic values of such constructions. Many strengthening techniques for the rehabilitation of existing monumental structures have been introduced. Some of these strategies are based on the application of fiber reinforced composite materials on the masonry surface. Among these, the application of FRP (Fiber Reinforced Polymers) is a low invasive retrofitting strategy able to improve both the in-plane and the out of plane masonry behaviour applicable to many different structural geometrical layouts. In this paper, by taking advantage of a parsimonious discrete element approach already introduced by the authors, a new strip macro-element for the interaction modeling between masonry elements and FRP reinforcement is proposed. This new element is able to provide a satisfactory simulation of the FRP layer applications toin masonry structures although maintaining a very low computational effort. In the paper, after a theoretical description of the proposed strategy, some numerical applications on case-studies, already investigated in the literature, highlight the capability of the proposed approach to properly describe the collapse behaviour of FRP reinforced masonry structures.(undefined)info:eu-repo/semantics/publishedVersio

Assessment of the seismic vulnerability of an unreinforced masonry structure based on discrete-macro dynamic analyses

UnReinforced Masonry (URM) structures experience severe damage due to in-plane and out-of-plane mechanisms when subjected to seismic actions. The assessment of the seismic vulnerability of URM generally requires complex analytical procedures consisting of the application of sophisticated numerical models. However, these models may request a high computational effort or may present an over-simplified scheme, mainly when the out-of-plane mechanisms are neglected. In this sense, a 3-dimensional macro-element model is here used for a preliminary assessment of the seismic vulnerability of a URM prototype characterized by an out-of-plane collapse mechanism. In this paper, the seismic vulnerability of this type of constructions is investigated by means of fragility functions in accordance with specific damage states and a given seismic input. The structural safety assessment was conducted by means of time history analyses with a limited computational effort. In addition, the evaluation of the limit states is here performed by means of an alternative approach named as Capacity Dominium based on the application of nonlinear static analyses.Peruvian Institution Innovate Perú/FINCyT (Fondo para la Innovación, Ciencia y Tecnología) through the PhD grant BECA-1-P-078-1