Advanced FE models of stiffened cleat angle connections

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.In this paper, the development of reliable 3D FE models of stiffened angle connections is dealt with. These advanced models will permit to obtain the assessment of the 3D deformational response of some future tests. Abaqus® finite element code was used to carry the 3D finite element analyses out. Symmetry was considered for these numerical analyses so a quarter of the geometry was modelled. The results obtained are compared with those from the analysis of the analogous specimens but without the top angle stiffener, showing an important increase in the initial connection stiffness. At the same time, the stress increment in the column panel zone due to the presence of the angle stiffener has been discussed

Mechanical stiffness prediction of beam-to-column stiffened angle joints

Manuscrito aceptado[Abstract]: Semi-rigid angle joints, in their different configurations, constitute a highly interesting alternative to other typologies like end plate joints. However, they are not widely used in the customary practice of European steel construction. The assembly of these joints is simple and cost effective, and they are a good choice in deconstruction and seismic designs. The stiffness of cleat angle joints can be increased either by preloading the bolts or by adding stiffeners to the angles. The development of theoretical models to evaluate both the stiffness and the resistance of these joints depends essentially on the existence of sufficient experimental evidence to validate them. Although there is already a reasonable number of tests on semi-rigid angle joints, this is not so in the case of joints with stiffened angles. Therefore, this study displays the results of experiments consisting of eight tests on stiffened angle joints. Moreover, an analytical model to predict the rotational stiffness, based on the Eurocode 3 Component Method according to a non-aligned model, is proposed. In this approach, a previously developed plate model is introduced to assess the axial stiffness of the top angle in bending. In addition, a new component that takes into account the stiffener in compression is presented. The proposed methodology is successfully validated with tests from the experimental work, as well as with previous tests from other researchers.Financial support provided by the Spanish Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional under contract BIA2016-80358-C2-2-P MINECO/FEDER UE is gratefully acknowledged

A new analytical formulation for the stiffness and resistance of the additional plate in bending in beam‐to‐beam steel joints

[Abstract] This paper focuses on the stiffness and resistance of the additional plate in bending. This is a component which appears in beam-to-beam bolted steel joints, when a secondary beam with a flush end plate is attached orthogonally to the primary beam by an additional plate welded between its flanges. In this work, six experimental tests have been carried out to calibrate a finite element model which has been used to develop a wide parametric study. Thus, a new formulation for stiffness and resistance based on an equivalent frame is proposed.The financial support provided by the Spanish Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional under contract BIA2016-80358-C2-2-P MINECO/FEDER UE is gratefully acknowledged

Artificial neural network prediction of the initial stiffness of semi-rigid beam-to-column connections

[Abstract]: Joints are significant components in the design and construction of steel structures. The characteristic parameters of the connections must be reproduced in a reliable way to represent the actual behaviour of a structure. Accordingly, the study of semi-rigid joints is essential to better understand this issue. Among the different types of semi-rigid joints, angle connections stand out as a suitable solution in many cases. This paper presents a methodology using artificial neural networks for predicting the initial rotational stiffness of major axis symmetrical angle connections according to the Eurocode description. A consistent stiffness database was developed from the existing data in the Steel Connection Data Bank. Then, the database was cleansed to provide with a robust training set. Different network architectures were analysed until a topology that showed a good performance and generalisation features was obtained. The network was successfully checked with some saved tests from the database and with off-database tests; the network could be reliably used within the range of the training input parameters.Ministerio de Ciencia e Innovación; PID2020-113895GBC3

Experimental evaluation, FEM and condensed stiffness matrices of 2D external welded haunched joints

Manuscrito aceptado[Abstract] In recent years, several researchers have been working hard to improve the knowledge with respect to steel joints behaviour. Special effort has been made for obtaining the stiffness of the different components of the joints, with the aim of introducing this stiffness in the component method in accordance with the EC3. Nevertheless, the component method has important limitations and therefore it is necessary to develop new methods for obtaining the stiffness of joints. In the present work, an alternative method of evaluating the stiffness of 2D external welded haunched joints is presented. The authors show the results of 4 tests and their corresponding finite element models. Four different typologies of joints have been tested, in regards to the stiffening of the column web. The four configurations of joints are the following: Joint 1: with three horizontal stiffeners in the column web. Joint 2: with two horizontal stiffeners and an inclined stiffener in the column web. Joint 3: with two horizontal stiffeners in the column web. Joint 4: without web stiffeners. In all cases, the specimens have been subjected to a point load at the end of the beam, and rotations and displacements have been measured. Additionally, finite element models of the joints have been developed, and they have been properly calibrated with the results obtained in the tests. The condensed stiffness matrices of the joints have been extracted, and they have been tested by means of introducing such matrices into the global analysis of 4 frames, and comparing the obtained results with those ones extracted from the corresponding finite element models. The use of the condensed matrix of the joints presents very good results, and takes into account all the interactions between the different degrees of freedom of the joint.The research described in this paper was financially supported by the Spanish Ministry of Economy and Competitiveness under contract BIA2016-80358-C2-2-P MINECO/FEDER, UE

Catalytic bi-reforming of methane for carbon dioxide ennoblement

6th International Conference on Energy and Environment Research (ICEER)New processes that may reduce the net carbon emissions and contribute to a more circular economy are needed. Bi-reforming of methane (BRM) is a promising method for syngas production, with a hydrogen-to-carbon monoxide ratio of two in the reaction products, relevant for example when the purpose is methanol synthesis. In this work, reaction studies were carried out over a nickel-based catalyst varying the temperature (798–1123 K). Three main temperature zones have been identified; a low temperature zone where the conversion of carbon dioxide is almost null, a middle temperature range where steam reforming of methane (SRM) is dominant while the conversion of carbon dioxide via dry reforming of methane (DRM) is low, and finally a high temperature range where DRM becomes more significant. The results show that syngas can be successfully produced using this process. For the range of operating conditions studied, the carbon dioxide and methane conversions increase with temperature, reaching 40% and 100%, respectively at the largest temperature studied. However, the production of syngas in a molar ratio of 1:2 for CO-to-H requires the use of high temperatures. Most probably the nickel agglomerates on top of the -alumina support are responsible for the poor catalyst performance.FCT, Portugal funded research grants SFRH/BPD/112003/2015, SFRH/BPD/105623/2015 and IF/01093/2014 and Center for Innovation in Engineering and Industrial Technology — CIETI, Portugal, UID/EQU/00305/2013. Project UID/EQU/00511/2019 - Laboratory for Process Engineering, Environment, Biotechnology and Energy — LEPABE funded by national funds through FCT/MCTES (PIDDAC), Portugal; Project “LEPABE-2-ECO-INNOVATION” – NORTE-01-0145-FEDER-000005, funded by Norte Portugal Regional Operational Programme (NORTE 2020), Portugal, under PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work was financially supported by: Associate Laboratory LSRE-LCM, Portugal – UID/EQU/50020/2019 – funded by national funds through FCT/MCTES (PIDDAC), Portugal .info:eu-repo/semantics/publishedVersio

A novel niobium (oxy)nitride-BaCe0.7Zr0.1Y0.2O3-δ composite electrode for Proton Ceramic Membrane Reactors (PCMRs)

The necessity to accelerate green and low carbon technologies, to mitigate the pending energetic crisis, potentiates the urgent search for alternative energy transfer methods. In this regard, Proton Ceramic Membrane Reactors (PCMRs) have shown great potential as a clean alternative for both energy production and the electrochemical synthesis of a wide range of chemical products. One of the most important is that of ammonia, where recent literature has demonstrated the potential use of PCMRs to either synthesize this chemical product or to use it as a fuel, and where suitable new electrodes must be developed. Hence, this work investigates the use of niobium (oxy)nitride (NbNxOy) in combination with proton ceramic conducting materials, as a new category of composite electrode for PCMRs applications. To achieve this goal, firstly, the chemical compatibility of the NbNxOy phase with the well-known proton conducting perovskite, yttrium-doped barium cerate (BaCe0.9Y0.1O3-δ, BCY10), was assessed. By X-ray powder diffraction, BaCe0.7Zr0.1Y0.2O3-δ (BCZY712) was shown to be chemically stable with the NbNxOy phase, surviving up to 850 °C, thus, facilitating the production of an electrolyte supported composite electrode film based on BCZY712-NbNxOy (40–60 vol%). Thermogravimetric experiments combined with X-ray diffraction were also made to assess the thermal stability of the NbNxOy material in both N2 and 2 % H2/N2 atmospheres, revealing that NbNxOy decomposes into its parent oxide in N2, while retaining the pure (oxy)nitride phase in the more reducing conditions. The polarization behavior of the BCZY712-NbNxOy composite electrode was evaluated by electrochemical impedance spectroscopy under different gaseous conditions of H2/N2 and NH3 atmospheres. The overall electrode mechanism was tentatively explained by three main steps, including i) proton incorporation/water release or adsorption/desorption of water, ii) gaseous hydrogen adsorption/desorption, and iii) interfacial transfer reaction of either protons or oxygen-ion vacancies. To the best of our knowledge, this is the first work that reports a detailed chemical compatibility study of niobium (oxy)nitride with a protonic ceramic matrix, while also outlining a detailed electrode mechanism under prospective conditions of hydrogenation/de‑hydrogenation of ammonia.publishe

Circulating microRNA changes in patients with impaired glucose regulation

© 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. We analysed if levels of four miRNAs would change after a lifestyle intervention involving dietary and exercises in prediabetes. MiRNAs previously shown to be associated with diabetes (Let-7a, Let-7e, miR-144 and miR-92a) were extracted from serum pre- and post-intervention. mRNA was extracted from fat-tissue for gene expression analyses. The intervention resulted in increased Let-7a and miR-92a. We found correlations between miRNAs and clinical variables (triglycerides, cholesterol, insulin, weight and BMI). We also found correlations between miRNAs and target genes, revealing a link between miR-92a and IGF system. A lifestyle intervention resulted in marked changes in miRNAs. The association of miRNAs with insulin and the IGF system (both receptors and binding proteins) may represent a mechanism of regulating IGFs metabolic actions

Experiencia de asistencia remota nunha asignatura base dunha enxeñería

[Resumo] Neste traballo reflíctese unha experiencia de asistencia remota nunha asignatura base dunha enxeñería. Trátase da asignatura Resistencia dos Materiais, impartida no segundo cuatrimestre en distintos graos no ámbito da enxeñería industrial. A teoría, boletíns de exercícios e prácticas de laboratorio impartíronse en modalidade asíncrona mediante videos breves realizados con ScreenCastOMatic, usando como repositorio a páxina de Moodle da asignatura. Asociado a cada tema había un cuestionario Moodle para reforzar a teoría. Realizouse unha programación síncrona de casos prácticos con un foro de dúbidas asociado. A avaliación constaba de exame final, cuestionarios e práctica de laboratorio. Os exercicios do exame abríanse paulatinamente en Moodle e resolvíanse a man para ser posteriormente escaneados e enviados via correo electrónico. As tutorías, resolvéronse síncronamente por correo electrónico. As incidencias foron pouco significativas, debidas maioritariamente á entrega do exame fóra do prazo establecido. Os resultados, vistos coa perspectiva de anos anteriores, foron excelentes non só pola elevada taxa de éxito, senon tamén pola baixa taxa de non presentados.[Abstract] This work reflects an experience of remote assistance in a basic subject of an engineering. The subject Mechanics of Materials, taught in the second semester in different degrees in the field of industrial engineering. The theory, exercise bulletins and laboratory practices were taught in asynchronous mode using short videos made with ScreenCastOMatic, using the subject's Moodle page as a repository. Associated with each topic was a Moodle questionnaire to reinforce the theory. A synchronous scheduling of case studies was conducted with an associated question forum. Tutorials were resolved synchronously by email. The assessment consisted of final exam, questionnaires and laboratory practice. The exam exercises were gradually opened in Moodle and solved by hand to be subsequently scanned and emailed. The incidences were insignificant, mainly due to the delivery of the exam outside the established deadline. The results, seen with the perspective of previous years, were excellent not only by the high success rate, but also by the low rate of not presenting.http://hdl.handle.net/2183/2879

Uso de test interactivos en la plataforma Moodle para una asignatura base de una ingeniería

[Resumen] La plataforma Moodle cuenta con interesantes herramientas que pueden resultar útiles a la hora de motivar al alumnado e incrementar la tasa de éxito asociada a una asignatura. El presente artículo muestra la experiencia del uso de la herramienta "prueba tipo test" de Moodle en una asignatura de segundo curso de una ingeniería. Tras haberse detectado un bajo seguimiento de la asignatura durante el curso, se tomó la decisión de complementar los boletines de prácticas con test teóricos que constaban básicamente de dos tipos de cuestiones: preguntas simples con un texto sencillo asociado y varias opciones de respuesta, y cuestiones gráficas donde el alumnado debe arrastrar el gráfico correcto a la cuestión requerida. Los test eran susceptibles de repetirse, quedando reflejados en la aplicación todos los intentos y el éxito o fracaso en cada uno de ellos. En un primer término, se decidió que la participación fuese voluntaria, confiando en obtener una atención razonable e incrementar por tanto el seguimiento de la asignatura. Tras una experiencia negativa, con posterioridad, se ofrecieron los test de nuevo como una opción voluntaria, pero advirtiendo al alumnado de que una de las cuestiones sería requerida en el examen. Este cambio incrementó la participación y, por consiguiente, el seguimiento de la asignatura como se demostrará en este trabajo. De la correlación entre alumnos participantes y aprobados en el examen final, puede extrapolarse un beneficio directo de esta medida, que invita a mantenerla y tal vez complementarla