Seismic behaviour and strengthening of existing reinforced concrete structures

The seismic vulnerability associated to existing reinforced concrete buildings, constructed until the late 1970’s, in urban areas of many European countries with moderate to high seismic hazard, is of extreme importance. In that period, reinforced concrete buildings were designed and constructed without considering adequately earthquake provisions, constituting therefore a significant source of risk for our cities. Recent major earthquakes around the world have evidenced that this type of existing buildings lacking appropriate seismic resisting characteristics are very vulnerable. The present paper focus in four important subjects regarding the seismic behaviour of reinforced concrete buildings, first the importance of the experimental studies on full-scale buildings in particular with two full-scale four-storey reinforced concrete frames tested, in these tests two problems were under study the presence on infill masonry panels in the structure and the use of smooth reinforcement bars, that induces a sudden loss of concrete-steel bond is one of the sources of brittle failure in RC elements. For the presence infill masonry panels it’s presented a simplified macro-model that is able of represents the global behaviour of infill masonry panels and its interaction with RC elements and its application to a case study. Regarding the study of RC buildings smooth reinforcement bars it’s presented the experimental campaign ongoing and the first results and conclusions. Another identified problem in the seismic behaviour of RC buildings is the behaviour of axially loaded reinforced concrete members under biaxial bending moment. It’s presented the actual lack of experimental studies and the nonexistence of simplified models able to represent these effects and the experimental study of RC columns under uniaxial and biaxial bending

Cyclic behaviour analysis of RC elements with plain reinforcing bars

The seismic performance of RC elements with plain reinforcing bars is particularly sensitive to the bond-slip mechanism. In this paper are described the cyclic tests performed on a two-spans beam with plain reinforcing bars and two beam-column joints with the same geometry and reinforcement detailing, one with plain reinforcing bars and the other with deformed bars. The main experimental results are presented and the comparison between the global behaviour of the two joints is established. A numerical model of the beam was developed within the OpenSees platform and calibrated with the experimental results. Particular attention was given to the bond-slip mechanism. Additional numerical analyses were developed without considering bond-slip. The comparison between the main numerical and experimental results shows the great importance of considering the bond-slip mechanism in the numerical models in order to have a precise simulation of the cyclic response of RC elements with plain reinforcing bars

Calibration of the numerical model of a freight railway vehicle based on experimental modal parameters

The simulation of the dynamic behavior of the train-track system is strongly dependent on the accuracy of the numerical models of the train and track subsystems. The use of calibrated numerical models of the railway vehicles, based on experimental data, enhances their ability to correctly reproduce the dynamic responses of the train under operational conditions. In this scope, studies involving the experimental calibration of freight wagon models are still scarce. This article aims to fill this gap by presenting an efficient methodology for the calibration of a numerical model of a freight railway wagon based on experimental modal parameters. A dynamic test was performed during the unloading operation of the train, adopting a dedicated approach which does not interfere with its tight operational schedule. From data collected during the dynamic test, five natural frequencies and mode shapes associated with rigid-body and flexural movements of the wagon platform were identified through the Enhanced Frequency-Domain Decomposition (EFDD) method. A detailed 3D finite-element (FE) model of the loaded freight wagon was developed, requiring precise knowledge of the vehicle design details which, in most situations, are difficult to obtain due to confidentiality reasons of the manufacturers. The model calibration was performed through an iterative method based on a genetic algorithm and allowed to obtain optimal values for seven numerical parameters related to the suspension’s stiffnesses and mass distribution. The stability of the parameters considering different initial populations demonstrated the robustness of the optimization algorithm. The average error of the natural frequencies decreased from 8.5% before calibration to 3.2% after calibration, and the average MAC values improved from 0.911 to 0.950, revealing a significant improvement of the initial numerical model.The authors would like to acknowledge the support of the Base Funding UIDB/04708/2020 and Programmatic Funding UIDP/04708/2020 of the CONSTRUCT (Instituto de I&D em Estruturas e Construções) funded by national funds through the FCT/MCTES (PIDDAC). The authors also express their gratitude to Dr. Nuno Pinto and Mr. Valdemar Luís, both technicians of LESE laboratory, for their indispensable assistance during the preparation and execution of the experimental testinfo:eu-repo/semantics/publishedVersio

Cold Urticaria and Infectious Mononucleosis in Children

Physical urticaria includes a heterogeneous group of disorders characterized by the development of urticarial lesions and/or angioedema after exposure to certain physical stimuli. The authors present the case of a child with severe acquired cold urticaria secondary to infectious mononucleosis. Avoidance of exposure to cold was recommended; prophylactic treatment with ketotifen and cetirizine was begun and a self-administered epinephrine kit was prescribed. The results of ice cube test and symptoms significantly improved. Physical urticaria, which involves complex pathogenesis, clinical course and therapy, may be potentially life threatening. Evaluation and diagnosis are especially important in children. To our knowledge this is the first description of persistent severe cold-induced urticaria associated with infectious mononucleosis in a child

Influência do mecanismo de aderência aço-betão no comportamento de elementos de betão armado com armadura lisa sujeitos a cargas cíclicas

Os efeitos da degradação da aderência aço-betão são particularmente importantes quando os elementos são sujeitos a cargas cíclicas e nos elementos construídos com armadura lisa, sendo esta uma das principais causas de dano e colapso de edifícios de betão armado quando sujeitos à acção dos sismos. Neste artigo são apresentados os resultados de um ensaio de uma viga de betão armado com armadura lisa, proveniente de uma estrutura existente, sujeita a cargas cíclicas. Estes resultados serão posteriormente comparados com os resultados do modelo numérico em desenvolvimento. O modelo pretende simular os resultados experimentais e terá em consideração os efeitos da degradação da aderência aço-betão, nomeadamente do escorregamento das armaduras

Caracterização experimental do comportamento de elementos estruturais parede-arco do Museu de Santa Joana em Aveiro

Com o objectivo de caracterizar o comportamento de elementos estruturais parede-arco do Museu de Aveiro, foram realizados ensaios laboratoriais e in situ, com vista ao desenvolvimento e calibração de um modelo numérico. A partir desse modelo foi possível estudar o comportamento deste tipo de elementos quando solicitado por cargas cíclicas. Foi assim possível aprofundar o conhecimento sobre os materiais usados na construção do Museu. Este artigo documenta os procedimentos adoptados e os resultados obtidos, quer dos ensaios, quer do modelo numérico

Food Allergy in Children - Data from an Allergy Outpatient Clinic

Estima-se que a prevalência de alergia alimentar nos países Ocidentais seja de cerca de 2 % na população geral e até 8% em crianças, não existindo dados concretos no que diz respeito a Portugal. Objectivos: Avaliar a prevalência de alergia alimentar e identificar os alergenos alimentares principais numa população de crianças observadas na Consulta de Imunoalergologia do Hospital de Dona Estefânia num período de 12 meses. Métodos: Foi feita uma revisão de registos clínicos dos 4879 doentes com idade igual ou inferior a 18 anos observados na Consulta durante o ano de 1998. O diagnóstico baseou-se na história clínica, testes cutâneos por prick e prova de provocação oral. Foram incluídos os casos de alergia alimentar clinicamente relevante nos últimos três anos de vida. Resultados: Foi identificada uma prevalência de alergia alimentar de 8,5% (414 casos, correspondendo a 477 quadros de alergia alimentar), sendo o alimento alergénico mais importante o leite, seguido por ovo e peixe. No subgrupo de crianças com idade superior a 12 anos o padrão foi bastante diferente, surgindo os crustáceos, o peixe, o amendoim, os frutos frescos e secos como principais alergenos. A maioria das crianças (83%) apresentou sensibilização a apenas um alimento. Clinicamente, predominaram os quadros de urticária e angioedema, seguidos por vómitos, diarreia e agravamento de dermite atópica. Conclusões: A população estudada apresenta uma prevalência de alergia alimentar de 8,5%, sendo de prever que seja inferior na população geral pediátrica. Será interessante complementar este estudo com dados obtidos noutros grupos etários, visando uma melhor identificação da prevalência de alergia alimentar e dos alergenos alimentares major no nosso país. É indispensável sensibilizar as entidades responsáveis pela regulamentação da indústria alimentar para a necessidade de uma melhoria a nível dos processos de fabrico e rotulagem no sentido de uma maior protecção do doente alérgico

Dynamic identification and seismic analysis of the "Serra do Pilar" monastery church

This paper presents part of the work developed for the seismic behavior study of an ancient structure, over 400 years old. The church structure was numerically modeled via the finite element method, using a three dimensional model with parameters calibrated by experimental testing. In situ and laboratory tests on extracted samples were performed, and dynamic tests were carried out for modal identification and structural stiffness calibration. The seismic analysis was performed in two calculation phases, under the action of artificially generated accelerograms representative of the local seismicity. Results of linear elastic dynamic calculations allowed the global behavior to be analyzed and provided the input for more detailed local analyses of structural parts where the non-linear behavior was considered. Finally, the seismic vulnerability of the structure is briefly addressed and discussed

Implementation of a fiber Bragg grating sensor network for structural monitoring of a new stone bridge

The implementation of a large sensing network based on fiber optic sensors forthe structural health monitoring of a new five arch stone bridge with a total span of 60 m overVizela River (Felgueiras, Portugal) is presented. In addition to the implemented instrumentationwith conventional sensors, four different types of fiber Bragg grating based sensors were speciallydeveloped for measuring temperature, strain and displacement in several critical points ofthe structure. In total, 85 Bragg sensors were installed and more than 800 m of fiber cables weredeployed along the bridge. The fiber optic sensing network installed on the bridge was entirelymonitored by using a single measurement unit designed for collecting and archiving the signalsfrom all the fiber Bragg grating sensors, and also to allow remote access to the important datathrough a standard GPRS connection