challenging aspects in removing the influence of environmental factors on modal parameter estimates

Abstract Modal based damage detection is a well-established procedure for Structural Health Monitoring (SHM) of civil structures. The development of robust algorithms for automated output-only modal parameter identification and tracking has renewed the interest towards modal based damage detection. However, the influence of environmental and operational variables on modal parameter estimates still represents a relevant shortcoming to their extensive use for SHM, because it can yield changes in the experimental estimates of the same order of magnitude of those induced by damage. As a consequence, there is the need to remove the effects of those factors in order to effectively detect damage. Different approaches can be adopted, some of which do not require measurements of the environmental and operational variable influencing the modal parameter estimates. Nevertheless, the effective removal of the environmental influence on modal parameters still remains a challenging aspect in SHM. In the present paper, different approaches for compensation of environmental effects are applied to a very large database of modal parameter estimates from a bridge in operational conditions. The objective of the paper is to investigate their performance under the concurrent influence of different environmental/operational variables (for instance, temperature and traffic) on modal parameter estimates. Static (effect on the estimate at time t depends only on the value of the variable at the same time instant) as well as dynamic (effect on the estimate at time t depends on the values of the variable at time t and also at previous time instants) methods are considered. The results of the study remark the relevance of identifying all sources of variability of the modal parameters in operational conditions

Operativna modalna analiza za određivanje svojstava povijesnih građevina

Assessing and reducing the seismic risks associated with historical structures require an appropriate knowledge of structural behaviour and characteristics, as suggested by recent national and international guidelines concerning cultural heritage. However, historical structures are characterised by a high level of uncertainty, which affects material properties and structural schemes and is related to deterioration processes or previous interventions and structural modifications. The level of knowledge can be increased by experimentally evaluating a structure’s dynamic properties, and the resultant data can be used to refine and update numerical models that are representative of the real structural behaviour. Moreover, the periodic monitoring of relevant parameters can help identify eventual deterioration phenomena. Thus, dynamic tests, in conjunction with model updating, are becoming reliable tools for non-destructively assessing historical structures. In this article, a brief discussion of the basic principles of dynamic identification under operational conditions is presented. Two tests with historical structures are then presented, and the main results are reported. The high performance of operational modal analysis techniques and the interesting opportunities these techniques provide for the structural assessment of historical structures are discussed.Ocjena i smanjenje seizmičkog rizika kod povijesnih građevina, zahtijevaju odgovarajuće poznavanje značajki ponašanja takvih konstrukcija, kako to sugeriraju nedavno objavljene nacionalne i međunarodne smjernice za građevine koje spadaju u kulturnu baštinu. Doduše, povijesne građevine su velika nepoznanica što se tiče svojstava materijala i konstrukcijskih sustava, a usto su podložne izmjenama, propadanju te promjenama tipa konstrukcije. Bolji uvid se može dobiti s procjenom dinamičkih svojstava modela konstrukcije, a dobiveni rezultati mogu se upotrijebiti za povećanje preciznosti i kvalitete numeričkih modela za realne konstrukcije. Štoviše, povremeno opažanje relevantnih parametara može pomoći identifikaciji možebitnih procesa propadanja. Zbog toga, dinamički pokusi, povezani s proračunskim modelima, postaju pouzdan alat kao nerazorne metode procjena stanja povijesnih građevina. U članku se razmatraju osnovna načela dinamičke identifikacije u uvjetima upotrebe konstrukcije. Opisana su dva pokusa na modelima povijesnih građevina, a prikazani su i najvažniji rezultati. Raspravlja se o velikoj djelotvornosti tehnike operativne modalne analize te o interesantnim mogućnostima koje ta tehnika pruža za procjenu povijesnih građevina

Some Remarks on Experimental Estimation of Damping for Seismic Design of Civil Constructions

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structural and seismic monitoring of the cardarelli hospital in campobasso

Abstract Recent earthquakes occurred in Italy and throughout the world have once again emphasized the critical role of health facilities for post-earthquake emergency management. Due to earthquake, several hospitals (L'Aquila 2009, Amatrice 2016) have lost their functionality because of damage to structural as well as non-structural members, equipment and installations. The primary role of hospitals after hazardous events requires the development of specific analysis and monitoring strategies aimed at quickly assessing their health conditions. Turning a hospital into a "Smart Health Facility" (SHF) allows remote assessment of the structural health; moreover, it can effectively support the mitigation of administrative and organizational vulnerability by acting on preparedness of the medical staff and supporting management and maintenance of structural as well as non-structural subsystems over time. Continuous monitoring of health and performance of hospitals can support the formulation of disaster mitigation plans and the definition of investment priorities to ensure the overall safety. In the present paper, some results of an on-going monitoring project for the main hospital in Campobasso (Southern Italy) are presented, focusing the attention on the response of the structure in operational conditions and after seismic events. Moreover, the results of experimental as well as operational modal analysis tests on a drug dispenser are discussed in order to assess their applicative perspectives for qualification of medical equipment in view of their seismic vulnerability assessment as non-structural elements

Automated Operational Modal Analysis and Its Applications in Structural Health Monitoring

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the role of the modal assurance criterion in the interpretation and validation of models for seismic analysis of architectural complexes

Abstract The seismic vulnerability assessment of historical buildings is usually a very complex task because of the large number of uncertainties in the characterization of their structural behaviour. The unique structural configurations, the adoption of old construction techniques and the presence of stratified structural modifications occurred over the centuries make the definition of an appropriate and reliable numerical model very challenging. The available analysis approaches distinguish the local response of selected macro elements from the global response of the structure. The problem of discriminating if the investigated structure shows a global behaviour or a local response has been often reported in the literature. However, the definition of a quantitative measure to discriminate the global modes from the local ones and, in the latter case, the associated macro elements, is currently missing. The Modal Assurance Criterion is a vector correlation index frequently used in experimental dynamics to quantify the similarity of mode shapes. In the present paper, it is used to define an original and quantitative approach to the discrimination between local and global modes. Results of application of the proposed procedure to an explanatory case study are reported, pointing out how the proposed method can guide towards the selection of the most appropriate analysis method

On BIM Interoperability via the IFC Standard: An Assessment from the Structural Engineering and Design Viewpoint

Building information modelling (BIM) plays a prominent role in a good deal of architecture, engineering and construction (AEC) works, envisaging a full transition to digitalization for the construction industry. This is also due to a number of national and international regulations regarding the design, erection, and management of civil engineering constructions. For this reason, full interoperability of software environments such as computer-aided design (CAD) and computer-aided engineering (CAE) is a necessary requirement, particularly when the exchange of information comes from different disciplines. Users, throughout the years, have faced CAD–CAE interoperability issues despite following the IFC neutral open file format. This inability to share data (CAD to CAD, CAD to CAE) often generates model-interpretation problems as well as a lack of parametric information and a disconnection of elements. This paper addresses issues and mapping mechanisms in the exchange of data for the purpose of defining a baseline for the current status of bidirectional data exchange between AEC CAD/CAE software via the IFC format. A benchmark study, covering three years of software releases is illustrated; the assessment of the software performance was made with reference to criteria associated with the software’s level of suitability for use of the structural models. Four classes of performance, depending on the accuracy of the data transfer and on the associated corrective actions to be taken, were adopted. This confirmed that at the moment, the implementation of the IFC standard by software manufacturers is geared towards an expert class of users. Further efforts are needed in order to ensure its application is adopted by a wider class, thus extending and regulating its use by national, regional, and local authorities

In-situ procjena zidanih svodova: Dinamička ispitivanja i numerička analiza

This paper concerns the structural identification of historical masonry buildings with reference to a case study, which is discussed in detail. The building is located in Southern Italy (Lecce). It has an ancient vaulted roof that is complex and commonly found in old masonry structures. This study takes advantage of extensive historical and structural investigations of the building. Preliminary activities have been conducted to obtain information about the current state of the structure including the geometry, morphology, structural details, material properties, prior interventions, and existing damage. This process was supported by an historical investigation into the conceptual background and construction methods used to build the structure. After the historical investigation, a series of experiments, including dynamic tests, were conducted on a number of the vaults to determine their dynamic response characteristics under operational conditions. A numerical model was also determined. In this paper, the primary dynamic test results and modelling assumptions are reported. Comparisons between numerical and experimental results are discussed.U ovom se članku razmatra konstrukcija jedne kulturno-povijesne zidane zgrade, detaljno obrađena još u jednoj ranijoj studiji. Zgrada se nalazi u Južnoj Italiji (Lecce). Zgrada ima složenu konstrukciju krova, sa svodovima, kakva je česta kod starih zidanih zgrada. U članku se uzimaju u obzir ranija opsežna povijesna i statička istraživanja. Ta ranija istraživanja bila su usmjerena ka dobivanju informacija o prethodnim ispitivanjima te o sadašnjem stanju konstrukcije, uključujući geometrijske karakteristike, oblikovnost, konstruktivne detalje, svojstva materijala i oštećenja zgrade. Pri tome su pomogla i ranija istraživanja o koncepciji i načinu gradnje zgrade. Nakon ovih istraživanja, obavljene su serije ispitivanja, između ostalog i dinamički pokusi na mnogim svodovima da se ustanove svojstva njihovog dinamičkog odziva u uvjetima standardne uporabe. Postavljen je i numerički model. U ovom su članku prikazani rezultati prvih dinamičkih ispitivanja i svojstava modela. Diskutira se odnos rezultata dobivenih numerički i eksperimentalno

Utjecaj DL-jabučne kiseline na metabolizam L-jabučne kiseline tijekom alkoholnog vrenja

Insufficient wine acidity can affect wine quality and stability. To overcome this problem, DL-malic acid can be added to the grape juice prior to fermentation. We have investigated the effect of DL-malic acid on wine fermentations and its influence on the final concentration of L-malic acid, naturally present in grape juice. To this end yeast strains that metabolise L-malic acid in different ways were tested and compared; namely, Schizosaccharomyces pombe (efficient L-malic acid degrader), Saccharomyces cerevisiae (non-degrader), hybrid strain S. cerevisiae x S. uvarum (intermediate degrader) and Saccharomyces uvarum (promoting L-malic acid synthesis). In all cases, D-malic acid passively entered the yeast cells and did not undergo malo-alcoholic fermentation. However, its presence in the juice, as a component of the mixture of D- and L- malic acid (DL-malic acid), reduced the amount of L-malic acid that can be degraded or synthesised by yeasts during malo-alcoholic fermentation.Nedovoljna kiselost vina može utjecati na njegovu kakvoću i stabilnost. Da bi se riješio taj problem, može se moštu prije vrenja dodati DL-jabučna kiselina. Ispitan je utjecaj DL-jabučne kiseline na fermentaciju vina i njezin utjecaj na konačnu koncentraciju L jabučne kiseline koja se nalazi u moštu. Stoga su ispitani i uspoređeni sojevi kvasca koji metaboliziraju L-jabučnu kiselinu, i to Schizosaccharomyces pombe (djelotvoran razgrađivač L-jabučne kiseline), S. cerevisiae (ne razgrađuje), hibridni soj S. cerevisiae x S. uvarum (djelomično razgrađuje) i S. uvarum (promotor sinteze jabučne kiseline). U svim slučajevima D-jabučna kiselina pasivno ulazi u stanice kvasca i ne provodi jabučno-alkoholno vrenje. Međutim, njezina prisutnost u grožđanom soku, kao dio smjese D- i L jabučne kiseline (DL-jabučna kiselina) snizuje količinu jabučne kiseline koja se može razgraditi ili sintetizirati s kvascima tijekom jabučno-alkoholnog vrenja

Inverse estimation of the local heat transfer coefficient in curved tubes: a numerical validation

Wall curvature represents one of the most used passive techniques to enhance convective heat transfer. The effectiveness of wall curvature is due to the fact that it gives origin to the centrifugal force: this phenomenon induces local maxima in the velocity distribution that locally increase the temperature gradients at the wall by then maximizing the heat transfer. This fact brings to a significant variation of the wall temperature and of the wall heat flux along the circumferential coordinate. The convective heat transfer coefficient is consequently not uniformly distributed along the tube's perimeter and is characterized by higher values at the extrados wall surface in comparison to the ones at the intrados wall surface. Therefore, for predicting the overall performance of heat transfer apparatuses that involve the use of curved tubes, it becomes important to know the local distribution of the convective heat transfer coefficient not only along the axis of the heat transfer section, but also on the internal tube's surface along the cross section circumference. The present paper is intended to the assessment of a procedure developed to evaluate the local convective heat transfer coefficient, along the circumferential coordinate, at the internal wall of a coiled pipe