•SHM of slender masonry elements: towers, minarets, chimneys and columns.•NDT of slender masonry elements: towers, minarets, chimneys and columns.•Experimental techniques on masonry towers, minarets, ...chimneys and columns.•OMA, AVT, numerical modeling and signal processing on slender masonry elements.•State of the art of dynamic identification of slender masonry elements.
The scientific community is hardly working to propose reliable methodologies of analysis and non-invasive technologies of investigation to assess the current state of conservation of historic buildings to verify their ability to resist future threats. These structures, mostly made of masonry, are difficult to assess due to the heterogeneity of materials and their mechanical behavior, but it is vital to preserve this invaluable cultural heritage by suitable structural assessment techniques. A great deal of research attention has been paid to monitoring their structural health; in many recent publications new advanced technological methods have been provided such as cheaper sensors, wireless connections, non-contact surveys and continuous monitoring. A bibliometric study has shown that more than half of the papers on Structural Health Monitoring (SHM) and Nondestructive Testing (NDT) on masonry have been published between 2018 and 2020, and 30% of those published in 2020 were on ‘slender’ elements like towers, chimneys or minarets. This paper presents a wide-ranging review of static and dynamic studies published on SHM and NDT of slender masonry structures summarizing and discussing the different experimental techniques used. With respect to the dynamic testing, Operational Modal Analysis (OMA) by accelerometers is the mostly frequent used technique by scholars, but other promising methods such as radar interferometry are also reported. This overall discussion is concluded with a short review of some examples on numerical structural health assessment and signal processing tools. An inclusive list of papers is provided describing the most important slender masonry structures characteristics, natural frequencies, experimental and numerical techniques employed and reference values. This paper, set on a practical perspective, is expected to be of interest to those researchers and practitioners who require an extensive and up-to-date review of this topic.
► We introduce a innovative approach for simulating nonlinear seismic response of masonry buildings. ► The computational cost of the proposed approach is greatly reduced, compared to nonlinear FEM. ► ...The basic plane element is able to reproduce the typical in-plane collapse behaviour of a masonry wall. ► This approach provides a powerful tool for the seismic assessment of masonry building. ► The model can be used for modelling large real structures in practical engineering.
The evaluation of the nonlinear seismic response of masonry buildings represents a subject of considerable importance whose resolution is nowadays a main research topic in earthquake engineering. Refined nonlinear finite element models require a huge computational cost that makes these methods unsuitable for practical application. In this paper an innovative discrete-element model, conceived for the simulation of the in-plane behaviour of masonry buildings, is presented. The basic idea of the proposed approach is to approximate the in-plane nonlinear response of masonry walls by an equivalent discrete element. This element is able to reproduce the typical in-plane collapse behaviour of a masonry wall subjected to earthquake loading. The reliability of the proposed approach has been evaluated by means of nonlinear incremental static analyses performed on masonry structures, for which theoretical and/or experimental results are available in the literature. The proposed computational strategy provides a relatively simple and practical tool which could be of significant value for the design and the vulnerability assessment of unreinforced masonry structures in seismic areas.
In the paper, the results of an experimental and numerical study on the out-of-plane bending effectiveness of a modern strengthening technique applied to existing masonry walls are presented. The ...technique consists in the application, on both wall faces, of a mortar coating reinforced with glass fiber-reinforced polymer (GFRP) meshes. Four point bending tests of full scale masonry samples (1000 width, 3000 mm height) were carried out considering three types of masonry (solid brick, 250 mm thick, rubble stone and cobblestones, 400 mm thick). The performances of plain and reinforced specimens were analysed and compared. It emerged that strengthened specimens are able to resist out-of-plane bending moments almost 4–5 times greater than those of plain specimens; moreover they can overcome deflections more than 25 times higher, due to the presence of the GFRP mesh, which contrasts the opening of cracks. The cracking and the ultimate bending moments of reinforced samples can be analytically predicted using relationships quite close to those used in the design of reinforced concrete beams subjected to combined axial and bending actions. The results of nonlinear static analyses performed on a 2D numerical model were also presented, so to comprehend the mechanical behaviour of reinforced masonry walls. Their agreement with the experimental results proved the reliability of the simulations; moreover, the extension of the 2D model to a 3D one, necessary to analyze the behavior of perforated walls, was also made.
Masonry structures are constructions made of discontinuous blocks that require unique numerical methods incorporating contact, friction, and cohesion models for their analysis. Given the large number ...of aging structures of this type still in use, there is a demand to combine these numerical methods with optimization algorithms to help in structural health monitoring. This paper combines discrete and finite methods with genetic algorithms for parametrizing two masonry structures. The first is a bridge with a large number of blocks, the material properties of which are estimated with a small error. Since the loads are low, the mortar’s properties are irrelevant. The second is a buried ogival vault; starting from only four pieces of experimental data from the literature and related with the failure loads, the material and contact properties are calculated. From them, many other failure loads are again iteratively calculated and favorably compared with the rest of the data. To further validate the inverse problem, the computed properties are used for several runs of the same vault but under different loads, obtaining again an almost perfect agreement with the experiments.
•Wall experimental crack simulated with FemDem getting same trend and 17% max. error.•Masonry bridge discretized with 212 blocks, 529 finite elements, 78 control nodes.•Young’s moduli, Poisson coef and density identified with only 2.3%, 4%, 2.2% errors.•Contact and material parameters optimized from global experimental results.•Ogival vault global experiment results fitted well with four conditions’ data.
The paper addresses two complex case studies of modal and structural identification of monuments in Portugal: the Clock Tower of Mogadouro and the Church of Jerónimos Monastery, in Lisbon. These are ...being monitored by University of Minho with vibration, temperature and relative air humidity sensors. Operational modal analysis is being used to estimate the modal parameters, followed by statistical analysis to evaluate the environmental effects on the dynamic response. The aim is to explore damage assessment in masonry structures at an early stage by vibration signatures, as a part of a health monitoring process that helps in the preservation of historical constructions. The paper presents the necessary preliminary dynamic analysis steps before the monitoring task, which includes installation of the monitoring system, system identification and subsequent FE model updating analysis, automatic modal identification and investigation of the influence of the environment on the identified modal parameters.
•Detailed survey of the 2019 Albanian tremors provides the base for the current study.•Masonry buildings are modelled through the Equivalent Frame approach.•Seismic capacities of the commonly used ...masonry typologies are estimated.•Nonlinear analyses are performed to assess the demand for the influential factors.•The performance is assessed by means of pushover analyses on four template buildings.
A Mw 6.4 earthquake hit the NW region of Albania on November 26, 2019, resulting in extensive damage to the civil structures in the broader area of Durrës city and its surroundings. According to the official statistics, it caused 51 death toll and ∼ 1.2 billion US dollars economic loses. This study investigates the seismic response of masonry buildings damaged during the earthquake. Four important typologies are selected to draw general conclusions from the performance analysis and damage assessment. A detailed field survey after the earthquake was conducted in Albanian territory to observe the impact on low and mid-rise buildings. Seven masonry buildings with 3 to 5 floors were chosen to represent the commonly constructed template designs. Mathematical models of each building were prepared in the light of experimental test results on the quality of structural wall components. Seismic displacement capacities of each building were estimated by pushover analysis. The significance of the findings was further explored by considering the inelastic response of a group of representative buildings during the 2019 Albania earthquake sequences. According to the analyses made, Near Collapse damage state may be reached at a PGA of 0.16 g for some type of buildings. At 0.26 g all considered buildings are expected to be either collapsed or at a near collapse stage. The expected PGA with a return period of 475 years is around 0.3 g and even reaches to 0.4 g in the region. Considering the analysis results, it can be said that decision makers should be aware of the catastrophic consequences of similar future events.
The present paper proposes a new methodology for the load-bearing capacity analysis of 2D masonry constructions by extending and reformulating the Continuous Airy-based for Stress Singularities ...(CASS) method, with a particular focus on the incorporation of volume forces, crucial to solve mechanical problems involving masonry constructions accurately. The masonry material is modelled using a Normal, Rigid, No-Tension (NRNT) model, largely adopted by the scientific community as material parameters, often unknowable, are not needed.
The load-bearing capacity problem is derived from an energy-based formulation and framed as a classic limit analysis approach, allowing for the direct determination of the maximum incremental load that a masonry structure can withstand, along with the corresponding internal stress pattern.
The structural domain is discretised with a simple finite element mesh, and the Airy stress potential is adopted to enforce the internal equilibrium directly. The boundary value problem is then solved as second-order cone programming (SOCP).
The CASS method is shown to offer modelling and computational advantages. Indeed, it accurately describes the mechanical response, including the ability to capture singular stress fields typically exhibited by masonry structures, particularly where cracks appear. The adoption of the Airy potential allows for a reduction in the number of explicit constraints from the problem. Moreover, the formulation of the boundary value problem as a SOCP ensures the existence of a unique load multiplier while offering computationally fast solutions even for large problems.
Several numerical examples are presented to demonstrate the CASS potential. Specifically, the ability to capture singular stress patterns diagonally crossing the finite elements showcases the CASS mesh independence, providing a straightforward approach to modelling complex geometries and loading conditions.
•Mesh-independent formulation for 2D seismic assessment of masonry façades.•Incorporation of volume forces into the CASS method.•Validation against experimental, analytical, and numerical solutions.•Singular stresses captured as concentrated on narrow bands.•The CASS method reveals the resisting compressive structure activated at the onset of collapse.
•The microseismical responses of three masonry structures during the construction process were measured.•The variations of the frequency, damping, and vulnerability of masonry structures were ...experimentally evaluated.•Two powerful signal processing techniques including FSR and RDM were employed.•The results indicated all abovementioned parameters have significantly improved during the construction process.•It can be insinuated that the NSCs has a considerable effect on the strength, solidity, and safety of the masonry structures.
The present paper focuses on the acquisition of the seismic responses of the masonry structures for evaluating the variations of the predominant frequency, damping ratio, and vulnerability index during their construction process. For this purpose, the seismic responses of three confined masonry structures against the ambient vibrations were acquired during their construction process in three sequential stages: (I) once their bearing walls in connection with the confined structural members and ceiling diaphragms were constructed; (II) once their partition walls in conjunction with plaster and mechanical equipment were performed; (III) once their facade and parapet elements in interaction with flooring and whitewashing were accomplished. Subsequently, the measured signals in accordance with the seismic responses of the masonry structures were processed through floor spectral ratio (FSR) and random decrement method (RDM) to exploit their predominant frequency, damping ratio, and vulnerability index in each individual stage. The measured seismic responses of three confined masonry structures demonstrated that the variations of the modal properties have substantially amplified throughout the construction process. Recursively, the vulnerability index has remarkably attenuated over entire stages. Ergo, it can be evolved that all aforementioned intrinsic characteristics of the studied masonry structures have significantly augmented during the construction process.
This paper presents a novel method for determining the fundamental frequency and modeling slender masonry structures, which is particularly relevant in the context of structural dynamics. This ...research evaluates the effectiveness of machine learning techniques, specifically artificial neural networks (ANN), and regression methods, including multiple linear regression (MLR) and multiple nonlinear regression (MNLR), in predicting the fundamental frequency of structures, considering both their geometrical and mechanical properties. The objective is to provide a comprehensive comparison of these methods, emphasizing their benefits, limitations, and potential applications in structural health monitoring. The ANN model demonstrated superior performance to linear and non linear regression methods. The findings could significantly impact both theoretical understanding and practical applications in this field. Moreover, this work paves the way for future research, potentially leading to the creation of more accurate and efficient predictive models for slender masonry structures. This methodology ensures a thorough understanding of the model’s behavior and its responsiveness to variations in input parameters.
•Comprehensive Database: Robust database of slender masonry structures’ characteristics.•Empirical Formulations: New empirical formulas for predicting slender structure frequencies.•ANN Model: ANN model for frequency prediction of slender masonry structures.•Parametric Analysis: Study on geometrical/mechanical parameters’ impact on frequency.•Future Research: Groundwork for refining models, ANN identified as the precise model.
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