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The paper delivers a short report about the modal identification carried out on a historical masonry palace in the city centre of L'Aquila, Palazzo Pica Alfieri, retrofitted after the 2009 earthquake. A concise description of the damage pattern and the retrofitting interventions heads the presentation of the results of the dynamic identification using Operational Modal Analysis. The identified mode shapes and natural frequencies drive a discussion about the detectability and the assessment of the modifications induced by the structural interventions using low-vibration measurements. Differently from more uncomplicated structures, the production of a Finite Element model representative of an existing masonry complex requires considerable efforts: the masonry structure may not behave like a continuum, due to the presence of cracks and unknown structural discontinuities. Still, the results of the dynamic identification bestow valuable information about the structural behaviour from a qualitative viewpoint, even if not backed by a faithful FE model. The paper addresses the aspects possibly related to the dynamic identification of a monumental masonry building, based on the shreds of evidence arisen from the presented case study. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on structural verification and proposed improvements for an ancient masonry arch bridge. The research encompasses multiple stages, starting with a detailed survey utilizing LiDAR and aerial techniques to collect precise data on the bridge's condition. Mechanical inspections assess deterioration levels and identify critical areas requiring attention. Based on the gathered data, a structural model of the bridge is developed, considering geometric parameters and material properties. The model undergoes rigorous verification procedures to assess its seismic response and ensure compliance with safety standards. The analysis includes identifying potential collapse mechanisms, such as the formation of plastic hinges, which can lead to structural failure. The study proposes structural improvements to enhance the bridge's performance and safety. These interventions specifically target vulnerabilities identified during the verification process. They include additional support elements, reinforcing critical areas, and utilizing advanced materials to improve tensile strength and durability. The feasibility of the proposed retrofitting solutions will be proved by performing a cost analysis, while environmental impacts are evaluated through an environmental assessment (Lifecycle Assessment — LCA) in which all the main bridge refurbishment phases have been included. Finally, some of the advantages of bridge refurbishment measures are shown by comparing the proposed intervention with a bridge reconstruction in terms of costs and environmental impacts. The outcomes of this study contribute to the existing knowledge on the rehabilitation of masonry arch bridges and serve as a valuable reference for engineers and practitioners involved in preserving architectural heritage. • Multi-stage digital assessment of an ancient masonry bridge. • Non-linear analysis to identify potential collapse mechanisms. • Study of the interventions to enhance the bridge's performance and safety. • Additional cost analysis and environmental assessment (LCA). • Comparison among the proposed interventions compared, and reconstruction. [ABSTRACT FROM AUTHOR]

Several baraccate houses, which date back to the eighteenth century, were discovered in the historical center of L'Aquila, Italy. Among traditional earthquake-resistant timber frames (T-F) in the Mediterranean Area, the baraccato of L'Aquila embodies an important step in the development of the baraccato technology. A significant variety of T-F structures emerged during the reconstruction works following the 2009 earthquake in L'Aquila. In the current paper, the diffusion as well as the different configurations of similar structures are reported. A systematic investigation of the baraccato was carried out; thus, a map of such structures has been drawn up. The baraccato aquilano does not unambiguously define a constructive typology, as in the baraccato borbonico, but it expresses the intuition-based attempt of master builders to protect masonry buildings from earthquakes. [ABSTRACT FROM AUTHOR]

The article focuses on the assessment of a structural intervention using a simple Bayesian approach driven by subspace-based indicators. A permanent monitoring system installed in a monumental masonry structure, the basilica of Santa Maria di Collemaggio in L'Aquila Italy, continuously acquires vibration data. The results of modal identification are first reported and discussed. Then, the article delivers a damage detection procedure, tested on two sets of data measured by the façade accelerometers before and after the CLT (Cross-Lam Timber) roof connection, which are interpreted as damage and reference states, respectively. The application of Bayesian inference to a set of damage indicators for the assessment of the façade structural modification is presented and compared with the results of a non-parametric χ 2 -tests. A computation procedure for the built of a statistical reference model is proposed by discussing the issue of the choice of the reference data set. [ABSTRACT FROM AUTHOR]

The seismic response of masonry monumental structures is a debated matter. In this paper, the authors compare the dynamic response of the Santa Maria di Collemaggio basilica under low-intensity earthquakes to the dynamic response under operational conditions. A permanent number of accelerometers records the dynamics of the Santa Maria di Collemaggio basilica under both operational and seismic excitation. It is questioned whether the earthquake intensity and the ambient parameters affect the modal parameters. The Least-Squares Complex Exponential (LSCE) method leads to the FRF function estimation. The stable frequencies identify the linear modal parameters which are likely to reproduce the seismic response. The authors endeavour to discuss whether the detected variations of the modal parameters are due to possible structural or material non-linearities. A time-frequency analysis confirms the results of the linear identification method. Further, the estimate of the dynamic amplification factors gives a glance over the global response by evidencing the possible existence of a macro-element response pattern. [ABSTRACT FROM AUTHOR]

This article attempts to describe a particular form of baraccata house, found in L'Aquila, Italy. The differences between this form of baraccato and the Italian traditional timber-framed (T-F) structures, the baraccato borbonico and the baraccato alla beneventana, are shown. In the upper valley of the Aterno river (Abruzzo, Italy), a few kilometers far from L'Aquila, wonderful 18th-century examples of T-F masonry structures are present. The use of wood pervades both the poor and noble buildings. In this article, the documentary and functional features of this peculiar anti-seismic timber-based building technique, which is widespread in L'Aquila and the neighboring areas, is described. After a comparative analysis of the technique's features, the case of three T-F buildings, belonging to three different social classes is reported, the first is the Ricci palace in Mopolino di Montereale, the second is a middle-class building, and the third is a rural one. The 1703 earthquake, which affected the upper valley of the Aterno river and the nearby city of L'Aquila, gave rise to an ante litteram anti-seismic culture. Timber was not seen as an obstacle to durability but a material to be exploited to protect buildings from earthquakes. [ABSTRACT FROM AUTHOR]

This paper focuses on the dynamic behaviour of a low-rise masonry building representing the Italian residential heritage through experimental and numerical analyses. The authors discuss an application of combined Operational Modal Analysis and Finite Element Model updating for indirect estimation of the structural parameters. Two ambient vibration tests were carried out to estimate the structure's dynamic behaviour in operational conditions. The first experimental setup consisted of accelerometers gathered in a row along the first floor to characterize the local dynamic of the floor. Conversely, the second setup had the accelerometers placed at the building's corners to characterize the global dynamics. The outcomes of the first setup were used to estimate the mechanical parameters of the floor, while the ones form the second were used to characterize the mechanical parameters of the masonry piers. Therefore, two finite element models were implemented: (i) a single beam with an equivalent section of the floor to grasp the local behaviour of the investigated horizontal structure; (ii) an equivalent frame model of the entire building to characterise the global dynamic behaviour. The model updating process was developed in two phases to seize local and global dynamic responses. The updated numerical model formed the basis for a sensitivity analysis using the modelling parameters. The authors chose to delve into the influence of the floor on the dynamic behaviour of low-rise masonry buildings. With this aim, non-linear dynamic analyses were carried out under different mechanical characteristics of floors, expressing the scatter for ordinary masonry buildings. The displacements' trends along the height of the building evidenced the notable role of the floor's stiffness in the non-linear dynamic behaviour of the building. Lastly, the authors derived the fragility curves predicting the seismic performance in failure probability under a highly severe damage state. [ABSTRACT FROM AUTHOR]

Masonry towers, located in seismic zones, are vulnerable and prone to damages up to compromise their stability. The scatter of data on the mechanical properties of masonry, geometry and boundary conditions determine a lack of building knowledge on their expected behaviour. Therefore the assessment of the seismic capacity represents a critical task. This paper contributes to the issue of seismic analysis of masonry towers, focusing a meaningful case study: the St.Silvestro belfry in L'Aquila, Italy. The tower, severely damaged by the 2009 earthquake sequence, underwent extensive restoration works, endeavoured to mitigate its vulnerability. The observed seismic damage, the performed no-destructive testing campaign and the accomplished rehabilitation measures are described in the paper. The authors appraised the actual seismic performances of the St.Silvestro belfry, reinforced by the last restoration works. At first, the Operational Modal Analysis (OMA) is carried out to enhance building knowledge. In a second step, a refined finite element model is calibrated on the results from OMA to seize the actual dynamic response. Ultimately, by using the updated finite element model, the authors estimate the fragility curves in terms of peak ground acceleration using truncated incremental dynamic analyses. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic characteristics and Finite element model updating of two confined masonry buildings in Messina, constructed in the aftermath of the devastating 1908 earthquake. The study addresses the need for advanced research in this field to enhance the understanding of the dynamic behaviour of confined masonry structures. The authors identified the modal parameters of the buildings from ambient vibration tests. Finite element models have been developed and fine-tuned in a second step to optimize the agreement between the simulated and observed modal parameters. The optimized parameters are then compared with the outcomes of nondestructive tests on masonry and reinforced concrete. This research addresses the modelling issues when dealing with confined masonry structures, offering guidance to engineers to select the modelling parameters. The paper emphasizes the substantial stiffening effect introduced by confined masonry, as evidenced by the optimized Young's modulus of masonry, which is almost two and a half times higher than values obtained from flat jack tests. To accurately represent the interaction between reinforced concrete ties and masonry panels within equivalent frame models, it becomes crucial to adequately overstate the masonry stiffness to capture the mutual coupling between structural components. • Dynamic characterization of confined masonry buildings. • Intelligent Automated Operational Modal Analysis approach. • Predictive capabilities of simplified FE modelling for confined masonry. • Genetic optimization algorithm to fine-tune modelling parameters. • Insight to select model parameters for confined masonry. [ABSTRACT FROM AUTHOR]

• An OLS operator may be an effective tool in processing seismic response data. • The proposed method allows the identification of possible non-stationary dynamic responses. • Correspondence between the mode shapes and natural frequencies obtained from the proposed method and those from Output Only identification. • Damping of masonry facades could be amplitude-dependent during the seismic event. • Masonry facades may exhibit a non stationary dynamic response even to low excitation levels. A low magnitude seismic response of a historical masonry structure, the Santa Maria di Collemaggio basilica, was acquired by a complex monitoring system. Ten FBA accelerometers, nine placed on the basilica facade and one on the ground level, recorded respectively the base accelerogram (Input) and the structural response (Output). By means of an elementary form of dynamic identification, based on an Ordinary Least Square operator (OLS), it has been attempted to identify the dynamic properties of the facade during the seismic event. The results, in terms of mode shapes, natural frequencies and damping factors, identified by the proposed Input-Output method, are compared with the ones identified under operational conditions. Despite the low intensity earthquake, the assumed linearity of the response has been investigated from further analysis on the acquired data. [ABSTRACT FROM AUTHOR]