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14. Comparative Analysis and Validation of Different Modulation Strategies for an Isolated DC-DC Dual Active Bridge Converter

Author

Coelho, Sergio, Sousa, Tiago J. C., Monteiro, Vitor, Machado, Luis, Afonso, Joao L., Couto, Carlos, Akan, Ozgur, Editorial Board Member, Bellavista, Paolo, Editorial Board Member, Cao, Jiannong, Editorial Board Member, Coulson, Geoffrey, Editorial Board Member, Dressler, Falko, Editorial Board Member, Ferrari, Domenico, Editorial Board Member, Gerla, Mario, Editorial Board Member, Kobayashi, Hisashi, Editorial Board Member, Palazzo, Sergio, Editorial Board Member, Sahni, Sartaj, Editorial Board Member, Shen, Xuemin (Sherman), Editorial Board Member, Stan, Mircea, Editorial Board Member, Jia, Xiaohua, Editorial Board Member, Zomaya, Albert Y., Editorial Board Member, Afonso, João L., editor, Monteiro, Vitor, editor, and Pinto, José Gabriel, editor

Published
2021
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19. Efficiency analysis of scientific laboratories

Author

Marcela do Carmo Silva, João Carlos C. B. Soares de Mello, Carlos Francisco Simões Gomes, and Isabella Couto Carlos

Subjects
Education (General), L7-991
Abstract

University laboratories involved with the teaching of science develop several intellectual property assets, offering to universities opportunities for investing in the scientific environment. Such feedback loop might be improved if investments in laboratories with high efficiency rates were analyzed and investigated. The purpose of this paper is to analyze how efficiency is taken into account in biomedicine, medicine and exact sciences laboratories to receive financial investments, through Data Envelopment Analysis (DEA); at the same time, it was possible to observe the low efficiency of some scientific laboratories, which indicates a need for improvement in the scientific environment to subsidize scientific research by using its own revenues.

Published
2020
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26. Parametric Study on the Buckling of Unbraced Steel Frames under Fire Situation.

Author

Silva, Thiago, Couto, Carlos, Vila Real, Paulo, and Lopes, Nuno

Subjects
STEEL framing, MECHANICAL buckling, FINITE element method, COLUMNS, HIGH temperatures, STEEL analysis, STRUCTURAL design
Abstract

A parametric investigation of several unbraced steel frames with regular and irregular geometry subjected to elevated temperatures is carried out in this study to determine the most accurate procedure and buckling lengths to be considered during the structural design under a fire situation. In such conditions, the stiffness and strength of steel decrease considerably due to high temperatures, and uncertainty remains in the application of the fire design rules of Eurocode 3 Part 1-2 (EN 1993-1-2) for unbraced frames as no information is given regarding the treatment of the deformed geometry (the so-called second-order effects). More precisely, it is unclear in the norm whether the verification based on the buckling length concept could be used or if a second-order analysis to calculate the internal forces is sufficient to ensure the stability of the frame in case of fire. Based on the linear buckling analysis of the steel frames accounting for the temperature development during a fire, recommendations for the appropriate buckling lengths to be used are given. Finally, it is demonstrated that using the recommended buckling lengths together with the design rules of EN 1993-1-2 leads to results in favor of safety when compared to the results obtained with the finite element method. On the other hand, it is concluded that using second-order internal forces and the real length of the columns as the buckling length, as suggested for room temperature design, yielded results outside safety when compared with the finite element method, and this analysis and verification procedure should not be used for the case of fire. [ABSTRACT FROM AUTHOR]

Published
2024
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35. Tópicos em Administração - Volume 17

Author

Cavalcante, Marta Celia Chaves, primary, Pinho, Renan Uchoa Gonçalves de, additional, Meirelles Junior, Julio Candido de, additional, Meirelles, Camyla D’Elyz do Amaral, additional, Gomes, Daniel Aparecido Cardoso, additional, Santiago, Wagner de Paulo, additional, Santos, Izael Oliveira, additional, Feitosa, Mônica Nascimento e, additional, Costa, Luciana Valus, additional, Oliveira, Claudimar Dias de, additional, Alves, Raquel Aparecida, additional, Lamenha, Artur Angelo Ramos, additional, Teixeira, Juedir Viana, additional, Ramos, André de Souza, additional, Nova, Adriana Lins de Gusmão Vila, additional, Melo, João Vinícius Santos Correia de, additional, Melo, Maria Luciana de, additional, Queiroz, David Marques de, additional, Lima, Gustavo Barbieri, additional, Garcia, Sheila Farias Alves, additional, Mello, Gabriella Trevisan de, additional, Carvalho, Cleide Luiza de, additional, Costa, Stella Regina Reis da, additional, Carvalho, Ana Luiza Rezende, additional, Pontes, Ana Valéria Vargas, additional, Couto, Carlos Henrique da Mota, additional, Horta, Patrícia Maia do Vale, additional, Oliveira, Victor Miranda de, additional, Zoppei, Rodrigo Azevedo, additional, Santos, Ismael Luiz dos, additional, Vinotti, Carlos Antônio, additional, Lustosa, Marllus de Melo, additional, Talmag, Ane Frank Araújo, additional, Souza, Francisca Sidma Ferreira de, additional, Rodrigues, Maxweel Veras, additional, Alves, Rafael Rodrigues, additional, Campos, Fernando Celso de, additional, Bomfim, Esrom Gustavo de Moura, additional, Carvalho, Deuciângela Ângelo, additional, Pessoa, Diana Maria da Silva, additional, Evangelista, Leilane Lima Almeida, additional, Sampaio, Marcelly Caldas, additional, Silva, Darlana Conceição da, additional, Lima, Rayra Brandão, additional, Tofoli, Eduardo Teraoka, additional, Santos, Eduardo Mauricio Porto, additional, Souza, Edmar Egidio Purcino de, additional, Santos, Camila Amorim Moura dos, additional, Rossi, Luiza, additional, Ignácio, Paulo Sérgio de Arruda, additional, Andrade, Diego Cesar Cavalcanti de, additional, Miyashita, Ricardo, additional, Lopes, Thiago Santos, additional, Santos, Iann Cavalcante dos, additional, Gambarato, Renato Luiz, additional, Santos, Silas da Silva, additional, Gambarato, Vivian Toledo Santos, additional, Bohm, Sandra Inês Horn, additional, Bohm, Geverson Tobias, additional, Gritti, Érico Tiago, additional, Silva Júnior, Everaldo, additional, Minadeo, Roberto, additional, and Teixeira, Moacir José, additional

Published
2019
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36. Tópicos em Administração - Volume 19

Author

Vieira, Emília Isabel Gomes, primary, Coelho, André Geraldo da Costa, additional, Coelho, Maria das Graças da Silva Costa, additional, Rodrigues, Daniel Lyra, additional, Mosquim, João Carlos, additional, Gollo, Silvana Saionara, additional, Krebs, Jean Filipe, additional, Silva, Angelita Freitas da, additional, Pavan, Luciana Maria Bernstein, additional, Pereira, David Barbalho, additional, Santos, Allison Haley dos, additional, Fonseca, Laura Maria Silveira da, additional, Singh, Ananda Silva, additional, De-Carli, Eduardo, additional, Oviedo, Ana Beatriz Murillo, additional, Orsiolli, Thálita Anny Estefanuto, additional, Lopes, Ana Paula Vilas Boas Viveiros, additional, Franchi, Giulianna, additional, Bonomi, Tatiana Montesso, additional, Pessanha, Thais Lopes, additional, Unghare, Anírian Cristiane, additional, Silva, Cremilce Barreto, additional, Fabião, Juliana Weber, additional, Mello, Simone Portella Teixeira de, additional, Almeida, Rogério da Silva, additional, Ferreira, Luciana Nunes, additional, Silva, Ingrid Moreno da, additional, Barreto, Caryna Paes, additional, Silva, Ivana Aparecida Ferrer, additional, Pantaleão, Elba de Oliveira, additional, Hirata, Simone, additional, Aguilar, Daniela Martina Alves, additional, Bauermeister, Valentina Santos, additional, Mazaro, Rita Eliana, additional, Moraes, Cecília Arlene, additional, Aguirre, Elisabet, additional, Lucena, Keiko Carolina Moraes Sasaki de, additional, Silva, Kamilla Clausen da, additional, Mendes, Victória Oliveira Santos Barbosa, additional, Mota, Júlia Maria Florentino da, additional, Paula, Alessandro Vinicius de, additional, Reis, Andrezza Vaz dos, additional, Souza, Patrícia Mara de, additional, Couto, Carlos Henrique da Mota, additional, Araújo, Ionara Coelho, additional, Melo, Ângela Cristina de, additional, Amorim, Gabriella Cristina de Melo, additional, deMoraes, José Nogueira, additional, Ribeiro, Claudete Fogliato, additional, Santos, Josseane Souza dos, additional, Thadani, Ramesh Mohan, additional, Rocha, Augusto César Barreto, additional, Lourenço, Victor Haruo Nitatori Rodrigues, additional, Sartorelli, Isabel Cristina, additional, Corrêa, Amanda Beatriz Nasatto, additional, Debroski, Bruna França, additional, Eyerkaufer, Marino Luiz, additional, Santos, Luana Fernandes dos, additional, Sousa Neto, Manoel Veras de, additional, Cosenza, Ana Margareth Moreira Mendes, additional, and Cosenza, Carlos Henrique Santana, additional

Published
2019
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37. Post-Earthquake Fire Assessment of Reinforced Concrete Frame Structures.

Author

Vitorino, Hugo, Real, Paulo Vila, Couto, Carlos, and Rodrigues, Hugo

Subjects
REINFORCED concrete, STRUCTURAL frames, EARTHQUAKE damage, SEISMIC event location, WILDFIRES, EARTHQUAKES
Abstract

Earthquakes can cause several catastrophic events and the consequences of fires in urban areas can be even worse than the consequences of the earthquake itself. Several numerical models were developed with SAFIR—software that models the behaviour of structures subject to fire for reinforced concrete (RC) frames to study their post-earthquake fire behaviour. First, a calibration was performed to validate the modelling strategy. Subsequently, two different frame typologies were considered, and a parametric study was carried out considering as the main variables the location and configuration of the damage caused by the earthquake and the location of the fire within the structure. The results show that the damaged RC frames have a lower fire resistance when compared with the undamaged frames. It was observed that the difference in time until collapse between an undamaged frame and a heavily damaged frame can be higher than 2 h. This observation is particularly relevant since, after a large earthquake, the rescue teams are generally overloaded, and consequently the response times are higher than that. This, combined with the reduction of the fire resistance of the reinforced concrete elements caused by the earthquake, can lead to increased severity and ultimately to the losses. [ABSTRACT FROM AUTHOR]

Published
2023
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40. Lateral-torsional buckling fire design of stainless steel I beams under combined end moments and transverse loads

Author

Lopes, Nuno, Couto, Carlos, Real, Paulo Vila, Camotim, Dinar, and Gonçalves, Rodrigo

Abstract

New design expressions for stainless steel laterally unrestrained beams under fire conditions have recently been proposed to be incorporated in the second-generation version of Eurocode 3 (EC3) – however, their merit assessment, in the context of beams acted by different bending moment diagrams, is still a relevant issue requiring investigation. Hence, this work presents a numerical study on the lateral-torsional buckling resistance of stainless steel I-beams with slender or non-slender cross-sections, when acted by different combinations of end moments and transverse concentrated or distributed loads at elevated temperatures. The safety and accuracy of the failure moment predictions provided by the EC3 design approaches (current and second-generation version) are assessed through the comparison with extensive numerical failure moment data, obtained with the ANSYS software. It is shown that these methodologies can be improved, as they may lead to overly conservative or unsafe failure moment estimates.

Published
2023
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41. Comparing analytical and machine-learning-based design methods for slender section steel members in fire

Author

Couto, Carlos, Tong, Qi, and Gernay, Thomas

Abstract

In thin-walled steel members, the complexity of the interaction between the buckling of the plates and the buckling of the member, combined with the reduction of steel properties with increasing temperature, hinders the development of simple accurate analytical models. As a result, analytical design methods tend to be overly conservative for simple situations, and inexistent for more complex situations such as temperature gradients and systems-level response, leading to unreliable fire design methods and affecting the attractiveness of these structures that are designed with optimization in mind. Meanwhile, data-based approaches using Machine Learning (ML) techniques have allowed overcoming complex nonlinear problems in various engineering disciplines. ML may provide fast models surpassing existing analytical methods and achieving accuracy similar to Finite Element-based solutions at much lower computational cost. While the development of ML models requires sophisticated modelling and large datasets, which may not always be available, once a ML model is developed its application to practical design situations within the limits of its validity is straightforward. This paper investigates opportunities from application of ML methods to the problem of thin-walled steel members in fire, including critical comparison of benefits and capabilities between ML methods and existing analytical approaches. With a dataset of 2304 data points for columns and 24516 for beams, the paper shows that ML models can outperform current state-of-the-art analytical models in terms of agreement with high-fidelity shell FE results.

Published
2023
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42. Influence of thermal gradients on the resistance of axially loaded steel columns subjected to localised fires

Author

Possidente, Luca, Couto, Carlos, Tondini, Nicola, and Real, Paulo Vila

Abstract

The definition of the resistance and the associated failure time of unprotected steel members in fire is crucial to the safety of steel structures. For this purpose, design standards allow for prescriptive approaches that rely on nominal fire curves that do not represent the physics of a real fire, for instance, a localised fire. Indeed, the thermal actions can be significantly different from the ones based on prescriptive approaches and non-negligible thermal gradients, both in the section and along the length, can develop in the structural members affecting the resistance of steel members. In this paper, three design procedures enabling increasing complexity of the temperature field were compared by investigating axially loaded steel columns characterised by a range of slenderness and load utilisation factors subjected to localised fires. The procedures consisted: i) in exploiting the recently proposed analytical LOCAFI model to compute single steel temperatures at different column heights and calculating the failure time with EN1993-1-2 considering the highest temperature; ii) in determining the failure time with beam finite element analyses in SAFIR by employing the temperatures at the different column heights, iii) in using a more refined version of the LOCAFI model included in SAFIR, which directly allows for the thermal gradients in the cross sections at the different heights of the column. The analysis showed that simplified procedures may predict both higher or lower failure times and therefore the employment of an advanced modelling is recommended.

Published
2023
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44. Machine learning models for the ultimate strength of steel beams – influence of bending moment diagram.

Author

Couto, Carlos and Real, Paulo Vila

Subjects
MACHINE learning, TORSIONAL load, ULTIMATE strength, BENDING moment, ARTIFICIAL neural networks, MECHANICAL engineering, PLASTIC analysis (Engineering), IRON & steel columns
Abstract

Artificial intelligence models using machine learning techniques are widely used in engineering to predict the mechanical behavior of structural members. Different machine learning (ML) algorithms such as artificial neural networks, random forests, and support vector regression were used to develop and train models in this study to predict the ultimate strength of steel beams, in particular that include the influence of the bending moment diagram on its lateral‐torsional buckling resistance. An extensive dataset was constructed using finite element analysis to obtain the ultimate strength of simply supported beams. A comparative study of different hyperparameters was carried out. The results show that the ML models outperform state‐of‐the‐art analytical models and that are able to capture the influence of bending moment diagrams. The limits of application of these ML models are explored, providing an overview of their potential use in designing real structures. [ABSTRACT FROM AUTHOR]

Published
2023
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