Application of a classification algorithm to the early-stage damage detection of a masonry arch

The early-stage identification of structural damage still represents a relevant challenge in civil engineering. Localized damages if not readily detected can lead to disruption or even collapse, involving hazard to people and economical losses. Although the final goal of the identification is to localize and quantify the damage, a reliable discrimination between normal and abnormal states of the structure in the very early stage of the damage onset is not an easy task. In the field of Structural Health Monitoring (SHM) great attention has been paid to the development of damage detection methods based on continuous and automatic registration of the system response to unknown ambient inputs. The numerical algorithms exploited must be: (1) easy to implement and computationally inexpensive, eventually being embedded in the sensors; (2) as much independent on human decision as possible; (3) robust to the many sources of uncertainties affecting the monitoring; (4) able to detect small damage extents in order to provide an early warning; (5) suitable for the application in the case of few and sparse measurements collected only in the normal condition. The performance of a novel version of Negative Selection Algorithm, recently developed by the authors, is here analyzed with attention to these issues. The algorithm is tested against data collected on a segmental masonry arch built in the laboratory of the University of Minho and subject to progressive lateral displacement of one support.- (undefined

An overview on structural health monitoring: From the current state-of-the-art to new bio-inspired sensing paradigms

In the last decades, the field of structural health monitoring (SHM) has grown exponentially. Yet, several technical constraints persist, which are preventing full realization of its potential. To upgrade current state-of-the-art technologies, researchers have started to look at nature’s creations giving rise to a new field called ‘biomimetics’, which operates across the border between living and non-living systems. The highly optimised and time-tested performance of biological assemblies keeps on inspiring the development of bio-inspired artificial counterparts that can potentially outperform conventional systems. After a critical appraisal on the current status of SHM, this paper presents a review of selected works related to neural, cochlea and immune-inspired algorithms implemented in the field of SHM, including a brief survey of the advancements of bio-inspired sensor technology for the purpose of SHM. In parallel to this engineering progress, a more in-depth understanding of the most suitable biological patterns to be transferred into multimodal SHM systems is fundamental to foster new scientific breakthroughs. Hence, grounded in the dissection of three selected human biological systems, a framework for new bio-inspired sensing paradigms aimed at guiding the identification of tailored attributes to transplant from nature to SHM is outlined.info:eu-repo/semantics/acceptedVersio

A Bio-inspired Framework for Highly Efficient Structural Health Monitoring and Vibration Analysis

Civil engineering structures are continuously exposed to the risk of damage whether due to ageing effects, excessive live loads or extreme events, such as earthquakes, blasts and cyclones. If not readily identified, damage will inevitably compromise the structural integrity, leading the system to stop operating and undergo in-depth interventions. The economic and social impacts associated with such an adverse condition can be significant, therefore effective methods able to early identify structural vulnerabilities are needed for these systems to keep meeting the required life-safety standards and avoid the impairment of their normal function. In this context, vibration-based analysis approaches play a leading role as they allow to detect structural faults which lie beneath the surface of the structure by identifying and quantifying anomalous changes in the system’s inherent vibration characteristics. However, although the considerable degree of maturity attained within the fields of experimental vibration analysis (EVA) and structural health monitoring (SHM), several technical issues still need to be addressed in order to ensure the successful implementation of these powerful tools for damage identification purposes. The scope of this paper is to present a bio-inspired framework for optimal structural health monitoring and vibration analysis. After a critical overview on current methods and tools, three main sources of bio-inspiration are described along with the relative algorithms derived for SHM applications. It is shown how uncovering the general principles behind the functioning of selected biological systems can foster the development of efficient solutions to the technical conflicts of actual SHM architectures and lead to new sensing paradigms for optimal network topology and sensors location. A compatibility-matrix is proposed to help compare biological and SHM systems and discriminate desired from unwanted features. Such a framework will ultimately assist in seeking for the most suitable nature-inspired solutions for more accurate condition screening and robust vibration analysis.FEDER funds through the Competitiveness Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633info:eu-repo/semantics/publishedVersio

Application of a bio-inspired anomaly detection algorithm for unsupervised SHM of a historic masonry church

Variations in dynamic properties are commonly used in Structural Health Monitoring to assess the conditions of a structural system, being these parameters sensitive to damage-induced changes. Yet, such variations can also be due to changes in environmental parameters, like fluctuations in temperature, humidity, etc. By performing a continuous monitoring, the correlation between those factors appears and their variations, if no damage exists, result in a cyclic phenomenon. Negative selection, a bio-inspired classification algorithm, can be exploited to distinguish anomalous from normal changes, thus eliminating the influence of environmental effects on the assessment of the structural condition. This algorithm can be trained to relate specific extracted features (e.g. modal frequencies) and other monitored parameters (e.g. environmental conditions), allowing to identify damage when the registered value oversteps the confidence interval defined around the predicted value. Negative selection draws inspiration from the mammalian immune system, whose physiology demonstrates the efficiency of this process in discriminating non-self elements, despite the restricted number of receptors available to face a vast amount of aggressors. In this paper, a negative-selection algorithm based on a non-random strategy for detector generation is optimized and tested on the monitoring data of a prominent monument of the Portuguese architecture.- (undefined

Modelado de paneles acústicos ranurados

El comportamiento acústico de un medio poroso común depende en gran medida de su porosidad abierta, consistiendo ésta en una red interconectada de poros que incluye porosidades cinemáticas y «sin salida». Una porosidad «sin salida» adecuadamente seleccionada puede ayudar a mejorar las propiedades de absorción acústica de dichos materiales gracias a los intercambios térmicos entre los fluidos en cada uno de estos poros. Este trabajo presenta un modelo que trata situaciones como las anteriores para el caso específico de paneles rígidos con orificios circulares dispuestos periódicamente y que contienen poros sin salida en forma de ranura. Para ello, se utilizan las soluciones analíticas que describen la propagación de ondas acústicas en poros de sección circular y en ranuras. Los resultados preliminares muestran la capacidad absorbente de estos sistemas, haciendo de ellos una interesante alternativa a las soluciones de panel perforado tradicionales. Además, el modelo demuestra ser una herramienta útil para estimar sus propiedades acústicas de una manera sencilla que también puede extenderse a otras geometrías.The acoustic behaviour of common porous media is highly dependent on their open porosity, this consisting of an interconnected network of pores including kinematic and dead-end porosities. A properly chosen dead-end porosity can help enhance the sound absorption properties of such materials because of the thermal exchanges between the fluids filling each of these pores. This work presents a model to deal with previous situations for the specific case of rigid panels with periodically arranged circular holes containing slit-like dead-end pores. Analytical solutions describing acoustic wave propagation in pores of circular cross-section and slits are used together to this end. Preliminary results show the absorption capability of these systems, making them an interesting alternative to traditional perforated panel solutions. Additionally, the model is proven to be a useful tool to estimate their acoustic properties in a simple manner that can also be extended to other geometry cases

Particle Swarm Optimization for damage identification in beam-like structures

The main objectives of Structural Health Monitoring (SHM) are the characterization and the assessment of the health condition of structural systems. Combined with appropriate Damage Identification (DI) strategies, SHM aims to provide reliable information about the localization and quantification of the structural damage by using an inverse formulation approach, with the damage parameters being estimated from parametric changes in dynamic properties. Mathematically, an inverse problem consists of the optimization of a function which represents the "distance" between the experimental and the numerically-simulated features of the system. Such process requires the development of a mock-up numerical model fairly representative of the system and iteratively updated until a response, as close as possible to the experimental one, is provided. The minimization of the difference between measured and predicted features' values is the objective function, whose global minimum corresponds to the best adjustment of the model variables. Metaheuristics represent a large class of global methods for optimization purposes able to outperformtraditional methods in the following aspects: ease of implementation, time consumption, suitability for non-linear phenomena, black-box and high-dimensional problems. The present paper analyses, through a numerical experimentation approach, the suitability of one of the best-known metaheuristics, i.e. the Particle Swarm Optimization (PSO) algorithm, for DI of beam-like structures. Modal properties are used to define the objective function and various algorithm instances are tested across different problem instances to assess robustness and influence of the algorithm parameters.This work was supported by FCT (Portuguese Foundation for Science and Technology), within ISISE, scholarship SFRH/BD/115188/2016. This work was also financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT - Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633

Normal incidence sound insulation provided by Sonic Crystal Acoustic Screens made from rigid scatterers - assessment of different simulation methods

[EN] Sonic crystal acoustic screens have been in progressive research and development in the last two decades as a technical solution for mitigating traffic noise. Their behaviour is quite different from that observed in classical barriers, with the latter being based on physically blocking the direct sound propagation path (only allowing diffracted noise to reach sensible receivers), and sonic crystals providing attenuation efficiency based on the creation of "band-gaps" at specific frequency ranges, due to the Bragg's interference phenomenon. The distinct physical mechanisms of these two types of noise barriers complicates the use of classical simplified or even numerical models developed for traditional barriers to simulate and predict the attenuation performance of a sonic crystal, and alternative methods become thus required. In the acoustics scientific literature, several authors have proposed estimation and simulation methods based on different numerical tools to predict the sound insulation provided by these new noise abatement solutions. This paper presents a comparative evaluation of some of these methods, with emphasis on the assessment of their accuracy versus memory usage in order to determine which one is the most suitable for optimization methodologies in the design of new devices with improved acoustic performance.M.P.P.T is grateful for the support of pre-doctoral Grant by the "Ministerio de Ciencia, Innovacion y Universidades. Agencia Estatal de Investigacion" of Spain through reference no. DI-15-08100. This work has been supported by the Ministerio de Ciencia, Innovacion y Universidades, Spain, under grant RTI2018-096904-B-I00. This work was developed within the scope of the project with reference POCI-01-0247-FEDER-033691 - HLS -Hybrid Log Shield, supported by FEDER funds, through Portugal-2020 (PT2020) Programme, within the scope of SII&DT System, and by POCI Programme. This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020.Peiró-Torres, M.; Ferri García, M.; Godinho, LM.; Amado-Mendes, P.; Vea-Folch, FJ.; Redondo, J. (2021). Normal incidence sound insulation provided by Sonic Crystal Acoustic Screens made from rigid scatterers - assessment of different simulation methods. Acta Acustica. 5:1-10. https://doi.org/10.1051/aacus/2021021110

EVOLUÇÃO DO CRÉDITO PESSOAL E HABITACIONAL NO BRASIL: UMA ANÁLISE DA INFLUÊNCIA DOS FATORES MACROECONÔMICOS NO PERÍODO PÓS-REAL

O estudo teve como objetivo central estudar a influência dos fatores macroeconômicos sobre a concessão do crédito pessoal e habitacional no período posterior à implantação do Plano Real. A escolha desses segmentos de crédito deve-se ao comportamento divergente dos volumes concedidos ao longo do período analisado, pois, enquanto se verificou expansão do crédito pessoal, o montante do crédito habitacional apresentou comportamento volátil, com tendência declinante. Para o alcance do objetivo, foram estimadas regressões individuais para ambos os tipos de crédito. Como resultado, obteve-se que o crédito pessoal foi mais suscetível a mudanças nas variáveis macroeconômicas, com mudanças de curto prazo, sendo influenciado, sobretudo positivamente pela formalização do emprego e negativamente pelo comportamento das taxas de juros e inflação. Já para o crédito habitacional, os reflexos das mudanças políticas foram mais efetivos no longo prazo; porém, devido à baixa significância das variáveis macroeconômicas, exceto a taxa de juros e a poupança, os resultados sugerem que o montante de crédito habitacional concedido pode , em grande medida, refletir questões conjunturais, como também decisões de política econômica

Comportamiento acústico del hormigón poroso. Caracterización mediante métodos experimentales e inversos

The use of porous concrete solutions with lightweight aggregates has become increasingly common in noise control due to their versatility in exterior and interior applications. In this work, samples of porous consolidated concrete with aggregates of expanded clay were produced, in order to study the influence of the grain size, thickness and water/aggregate/cement ratio on the sound absorption. Experimental techniques were used to obtain the surface impedance and sound absorption coefficient. In addition to experimental characterizations, an inverse method was used (based on a genetic algorithm) to obtain the macroscopic parameters capable of representing the materials studied through the theoretical model of Horoshenkov-Swift. Using the theoretical Horoshenkhov-Swift model it becomes possible to represent these materials in numerical models as equivalent fluids.El uso de soluciones basadas en hormigón poroso con agregados ligeros se ha vuelto cada vez más común en el ámbito del control de ruido debido a su versatilidad en aplicaciones exteriores e interiores. En este trabajo, se han preparado muestras de hormigón poroso con agregados de arcilla expandida, para estudiar la influencia del tamaño de grano, el espesor y la relación agua / agregado / cemento en la absorción de sonido. Se han utilizado técnicas experimentales para obtener la impedancia superficial y el coeficiente de absorción de sonido. Además de las caracterizaciones experimentales, se ha aplicado un método inverso (basado en un algoritmo genético) para obtener los parámetros macroscópicos capaces de representar los materiales estudiados a través del modelo teórico de Horoshenkov-Swift. Mediante el modelo teórico de Horoshenkhov-Swift, es posible representar estos materiales en modelos numéricos como fluidos equivalentes.This work was developed within the scope of the POCI-01-0247-FEDER-033990 (iNBRail) Project, funded by FEDER funds through COMPETE 2020, Portugal 2020. This work was also supported by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633 and through the Regional Operational Programme CENTRO2020 within the scope of the project CENTRO-01-0145-FEDER-000006. The support of COST (European Cooperation in Science and Technology) through the COST Action CA15125 – DENORMS: “Designs for Noise Reducing Materials and Structures” is here also acknowledged

An overview on nature-inspired optimization algorithms for Structural Health Monitoring of historical buildings

Structural Health Monitoring (SHM) of historical building is an emerging field of research aimed at the development of strategies for on-line assessment of structural condition and identification of damage in the earliest stage. Built heritage is weak against operational and environmental condition and preservation must guarantee minimum repair and non-intrusiveness. SHM provides a cost-effective management and maintenance allowing prevention and prioritization of the interventions. Recently, in computer science, mimicking nature to address complex problems is becoming more frequent. Nature-inspired approaches turn out to be extremely efficient in facing optimization, commonly used to analyze engineering processes in SHM, providing interesting advantages when compared with classic methods. This paper begins with an introduction to Natural Computing. Then, focusing on its applications to SHM, possible improvements in built heritage conservation are shown and discussed suggesting a general framework for safety assessment and damage identification of existing structures.This work was financed by FEDER funds through the Competitiveness Factors Operational Programme COMPETE and by national funds through FCT - Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633info:eu-repo/semantics/publishedVersio