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This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of Architectural Heritage on 2022, available online at: http://www.tandfonline.com/10.1080/15583058.2022.2096513 This paper presents the historical development of the vertical extensions of unreinforced masonry buildings in the Eixample district of Barcelona and their impact on the seismic behaviour. Existing masonry buildings of Eixample present significant seismic risk because, despite the low to moderate seismic hazard of Barcelona, they show a marked vulnerability given their average height of six storeys and the substantial slenderness of the walls. Between the end of the 19th century and the beginning of the 20th century, the vertical extensions, known as remuntes in Catalan, were a common solution to the increasing demographic demand of the city. In their majority, these vertical extensions add a structural irregularity that represents a potential vulnerability factor not yet investigated. The present study focuses on Eixample’s remuntes, including their historical development, the description of their structural features, and the identification of their most representative configurations in the existing building stock. A seismic analysis based on the Finite Element Method is presented on a reference model without extensions and three others with the most recurrent configurations of remuntes. The seismic response is investigated through pushover analysis. The results provide a better understanding of the negative impact of the vertical extensions on the seismic performance. This work was supported by the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU) [RTI2018-099589-B-I00], the State Agency of Research (AEI) [RTI2018-099589-B-I00] and the European Regional Development Fund [RTI2018-099589-B-I00]; through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres [RTI2018-099589-B-I00]; Agència de Gestió d'Ajuts Universitaris i de Recerca; MSc SAHC Consortium scholarship; Sapienza University of Rome.

Trabajar en proyectos que lidien con estructuras históricas conlleva una serie de desafíos específicos que resultan de tratar de encontrar un equilibrio entre el respeto a los principios de conservación del patrimonio y garantizar la seguridad estructural. El principal problema es que, en muchas ocasiones, la información existente sobre la estructura es poca o ninguna. Las incógnitas e incertidumbres sobre la estructura existente pueden estar relacionados con muchos aspectos, desde los materiales de construcción hasta las conexiones entre elementos estructurales. El éxito de cualquier intervención en el edificio patrimonial, sea una medida de refuerzo local o rehabilitación más extensa, dependerá en gran medida del buen entendimiento de las incógnitas y problemas específicos de la estructura. Con ese fin, es esencial conocer las herramientas disponibles para obtener información relevante sobre la estructura que, dadas las características patrimoniales, deben ser poco o nada invasivas. Este artículo presenta algunas preguntas comunes relacionadas con el diagnóstico estructural que suelen surgir en un proyecto de conservación. Usando casos de estudio, el artículo analiza la aplicabilidad de diferentes herramientas, específicamente varios tipos de ensayos no destructivos y varios métodos de análisis estructural, para tratar de contestar a dichas preguntas.

The out-of-plane response is a complex and at the same time key aspect of the seismic vulnerability of masonry structures. It depends on several factors, some of which are the material properties, the quality of the walls, the geometry of the structure, the connections between structural elements and the stiffness of the diaphragms. During the last years, a wide variety of numerical methods has been employed to assess the out-of-plane behaviour of unreinforced masonry structures. Finite element macro-modelling approaches are among the most famous as they allow modelling large structures at a reasonable computational cost. However, macro-modelling approaches may result in a non-realistic representation of localized cracks and a dependency of the numerical solution on the finite element mesh. Mixed strain/displacement finite elements have been recently proposed as a remedy to the above nu-merical pathologies. Due to the independent interpolation of strains and displacements these finite element formulations are characterized by an enhanced accuracy in strain localization and crack propagation problems, being at the same time practically mesh independent. For these reasons, mixed finite elements are employed in this work for the out-of-plane assessment of unreinforced masonry struc-tures, being at the same time their first real-scale application. A full-scale experimental campaign of two masonry structures, a stone and a brick one, subjected to shaking-table tests is chosen as reference benchmark. Their structural response under seismic actions is numerically assessed through nonlinear static analysis. The proposed approach is validated through the comparison of the numerical results with the experimental ones, as well as with the results obtained using standard irreducible finite ele-ments.

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29CF.1943-5509.0001494. This paper presents the systematic use of numerical analysis as a tool for addressing some of the most common challenges encountered in the structural analysis of complex historical masonry structures, i.e. the description of the effects of history-related phenomena and the un-certainty of material properties. The numerical strategy is based on the use of a constitutive model able to describe time-dependent strain accumulation, as well as damaging behaviour un-der different stress states. This constitutive model is combined with a crack-tracking technique to represent tensile crack localization. The numerical model is applied to the study of two im-portant monuments in Spain, i.e. the Mallorca Cathedral and the church of the Poblet Monas-tery. The staged construction analysis of the first case study allows understanding the reasons of its current deformed condition, i.e. critical construction process, strain accumulation given by long-term creep phenomena, and nonlinear geometric effects. The structural analysis of the second case study allows the structural diagnosis of the existing deformation and cracking pat-terns given by architectural alterations, insufficient buttressing of the naves, and past earth-quakes. The application of a probabilistic analysis to the church of the Poblet monastery allows considering the effects of the uncertainties of material properties and numerical parameters in the seismic vulnerability assessment. The authors would like to thank the Ministry of Science, Innovation and Universities (MCIU) of the Spanish Government, the State Agency of Research (AEI) and the European Regional Development Fund (ERDF) through the SEVERUS project (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban cen-tres ref. num. RTI2018-099589-BI00).

The final publication is available at Springer via http://dx.doi.org/10.1007/s00466-016-1351-6 Tracking algorithms constitute an efficient numerical technique for modelling fracture in quasi-brittle materials. They succeed in representing localized cracks in the numerical model without mesh-induced directional bias. Currently available tracking algorithms have an important limitation: cracking originates either from the boundary of the discretized domain or from predefined “crack-root” elements and then propagates along one orientation. This paper aims to circumvent this drawback by proposing a novel tracking algorithm that can simulate cracking starting at any point of the mesh and propagating along one or two orientations. This enhancement allows the simulation of structural case-studies experiencing multiple cracking. The proposed approach is validated through the simulation of a benchmark example and an experimentally tested structural frame under in-plane loading. Mesh-bias independency of the numerical solution, computational cost and predicted collapse mechanisms with and without the tracking algorithm are discussed.

Existing heritage structures are frequently composed of diverse masonry typologies, corresponding either to various structural members (e.g. arches, walls, piers) or to additions constructed in different eras. The identification of the material properties of the different masonry typologies is usually demanding due to the high cost of the necessary specialized in-situ experimental testing procedures and to the restrictions posed by the cultural value of historical buildings. This lack of information underlines the importance of probabilistic studies considering the uncertainties connected with the evaluation of the material properties. Such activities become essential in studies dealing with the conservation of built cultural heritage against hazardous events, such as earthquakes. This work investigates the seismic vulnerability assessment of large monumental structures with complex geometry. The church of Santa Maria del Mar in Barcelona is considered as a case study, and a representative macro-element of the bay structure is studied against in-plane horizontal loading through pushover analysis. A Monte Carlo simulation is used to estimate the effect of the uncertainties on the material properties, which are considered as random variables. The developed fragility curves express the safety level and the damage expected on the structure for different seismic hazard scenarios.

The present paper showcases the work carried out as part of the seismic retrofit of the Ottoman fortress of Gjirokastra, a UNESCO World Heritage site located in Albania. The need for strengthening and retrofitting the structure stems from the fact that it is situated in a region of high seismicity and showed signs of structural distress at the time of investigation. The hill on which the castle is built also has stability issues. The seismic retrofit focused on a damaged stone masonry tower of the fortress and was designed following a comprehensive methodology for the inspection, diagnosis and geotechnical and structural analyses. Through the use of non-destructive tests, the existing soil conditions, the material properties and composition and the dynamic behaviour of the tower were assessed. Nonlinear finite element analysis was used to establish the cause of the existing damage and to determine the most effective strengthening solutions. The findings of the investigation revealed potential causes of the observed damage as well as the need to carry out retrofitting works at the tower beyond ground improvement solutions to bring the performance of the structure up to the code-specified level. This paper highlights the importance of planning and coordination between all the relevant disciplines involved in the project, so that apt inspection and diagnostic tools can be used to fill in the gaps where information is missing and to design optimal and integrated structural interventions in historic structures. Satisfactory seismic performance can be obtained by using a combination of retrofitting techniques, which specifically target the weak elements identified via the analyses.

This paper presents an improved computational model for the analysis of masonry structures based on continuum mechanics finite element approaches. The proposed numerical technique uses a cracktracking algorithm to model the formation of strain localization bands within the discretization domain. This strategy results in two major benefits. First, the representation of the discrete cracks experienced by masonry structural elements is more accurate and consistent with limit analysis, which in turn leads to the realistic prediction of the collapse mechanisms. Second, the numerical solution is mesh-bias independent ensuring the objectivity of the simulation to the direction of the utilized mesh. The efficiency of the proposed algorithm is illustrated through the numerical simulation of a selected experimental test on a masonry pier-spandrel system.

The final publication is available at Springer via http://dx.doi.org/10.1007/s11831-018-9274-3 The importance of crack propagation in the structural behaviour of concrete and masonry structures has led to the development of a wide range of finite element methods for crack simulation. A common standpoint in many of them is the use of tracking algorithms, which identify and designate the location of cracks within the analysed structure. In this way, the crack modelling techniques, smeared or discrete, are applied only to a restricted part of the discretized domain. This paper presents a review of finite element approaches to cracking focusing on the development and use of tracking algorithms. These are presented in four categories according to the information necessary for the definition and storage of the crack-path. In addition to that, the most utilised criteria for the selection of the crack propagation direction are summarized. The various algorithmic issues involved in the development of a tracking algorithm are discussed through the presentation of a local tracking algorithm based on the smeared crack approach. Challenges such as the modelling of arbitrary and multiple cracks propagating towards more than one direction, as well as multi-directional and intersecting cracking, are detailed. The presented numerical model is applied to the analysis of small- and large-scale masonry and concrete structures under monotonic and cyclic loading.

This paper presents a procedure for the extension of the Vulnerability Index Method (VIM) to the seismic assessment of hybrid timber–masonry buildings. The research is based on the execution of a detailed numerical study of this peculiar structural typology to identify the classes and calibrate the scores assigned to influential vulnerability parameters, namely the irregularities of the structural system, the type of floor, and the state of conservation of the building. A sensitivity analysis of the seismic capacity is developed by performing pushover analyses with several models corresponding to realistic variations of each structural or material parameter. The seismic performance of the buildings is analysed by the N2 Method. This methodology leads to the proposal of a new calibrated vulnerability index form that, together with those existing in literature for masonry and reinforced concrete structures, can be used for the seismic assessment of heterogeneous urban environments. The proposed VIM is applied to the assessment of 111 buildings located in the historical centre of the city of Valparaíso, Chile. The computation of the vulnerability index allows a fast evaluation of the seismic vulnerability of the urban buildings. The results plotted on vulnerability maps built within a GIS environment allows the assessment of the impact of potential collapses on the serviceability of two emergency evacuation routes included in the civil protection plans of the city. The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI), as well as the ERDF (European Regional Development Fund), through the SEVERUS project (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. num. RTI2018-099589-B-I00). The first author gratefully acknowledges the ELARCH project (Euro-Latin America partnership in natural Risk Mitigation and protection of the Cultural Heritage, reference number 552129-EM-1-2014-1-IT- ERASMUS MUNDUS EMA21), funded by the European Commission, for the financial support of her predoctoral grant. Peer Reviewed Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.1 - Per a 2030, assegurar l’accés de totes les persones a habitatges i a serveis bàsics adequats, segurs i assequibles, i millorar els barris marginal Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.3 - Per a 2030, augmentar la urbanització inclusiva i sostenible, així com la capacitat de planificar i gestionar de manera participativa, integrada i sostenible els assentaments humans a tots els països Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del món Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.5 - Per a 2030, reduir de forma significativa el nombre de morts causades per desastres, inclosos els relacio­nats amb l’aigua, i de persones afectades per aquests, i reduir substancialment les pèrdues econòmiques directes causades per desastres relacionades amb el producte interior brut mundial, fent un èmfasi especial en la protecció de les persones pobres i de les persones en situacions de vulnerabilitat Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.b - Per a 2020, augmentar substancialment el nombre de ciutats i assentaments humans que adopten i posen en marxa polítiques i plans integrats per promoure la inclusió, l’ús eficient dels recursos, la mitigació del canvi climàtic i l’adaptació a aquest, així com la resiliència davant dels desastres, i desenvolupar i posar en pràctica una gestió integral dels riscos de desastre a tots els nivells, d’acord amb el Marc de Sendai per a la reducció del risc de desastres 2015.2030 Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.c - Proporcionar suport als països menys avançats, incloent una assistència financera i tècnica, perquè puguin construir edificis sostenibles i resilients utilitzant materials locals Objectius de Desenvolupament Sostenible::13 - Acció per al Clima Objectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els països Objectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.2 - Incorporar mesures relatives al canvi climàtic en les polítiques, les estratègies i els plans nacionals Objectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.3 - Millorar l’educació, la conscienciació i la capacitat humana i institucional en relació amb la mitigació del canvi climàtic, l’adaptació a aquest, la reducció dels efectes i l’alerta primerenca