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- Comportamento cíclico de ligações metálicasPublication . Nogueiro, PedroO interesse da investigação do comportamento de estruturas metálicas solicitadas a acções sísmicas é um tema actual constantemente lembrado por notícias que nos mostram a ocorrência frequente de sismos nas mais diversas regiões do mundo. Neste trabalho de doutoramento, descreve-se a execução de um programa experimental de ensaios de ligações metálicas à escala real, dividido em quatro séries totalizando um total de 13 ensaios, solicitados a acções cíclicas. Procurou-se com este programa de ensaios, conhecer e caracterizar o comportamento real das ligações ensaiadas. Paralelamente ao trabalho experimental, desenvolveu-se a implementação numérica de um modelo matemático, que permite simular o comportamento real das ligações metálicas. Este modelo foi incorporado num software de cálculo automático, para assim ser possível o estudo e análise da contribuição do comportamento real das ligações no comportamento global da estrutura. Os ensaios experimentais levados a cabo neste trabalho, a par dos ensaios experimentais desenvolvidos por outros autores, permitiram definir os parâmetros de calibração do modelo implementado. Por fim, e com base no trabalho desenvolvido, estudou-se a influência do comportamento real das ligações no desempenho sísmico de três estruturas metálicas solicitadas a acções sísmicas.
- Influência do comportamento real das ligações em pórticos metálicos de travessas inclinadasPublication . Nogueiro, PedroO objectivo deste trabalho consiste em estudar a influência do comportamento real das ligações em pórticos de travessas inclinadas. Todo o trabalho desenvolvido assenta na elaboração de análises: (i) elástica de 1.ª ordem, (ii) linear de estabilidade (cargas críticas), (iii) elástica de 2.ª ordem, (iv) elasto-plástica de 1.ª ordem e (v) elasto-plástica de 2.ª ordem, aplicadas a pórticos metálicos de travessas inclinadas. A estratégia seguida baseia-se no estudo do comportamento de pórticos metálicos, simulando a rigidez das ligações, através de uma lei de comportamento bi-linear. A rigidez atribuída a cada uma das ligações é alterada ao longo de cada análise, consoante se trate de uma ligação rotulada, semi-rígida ou rígida. Aplicam-se todas as análises, depois de devidamente calibradas, a um pórtico base (PB), apresentando-se logo de seguida os resultados de um estudo paramétrico mais abrangente, quer em gama estrutural quer em estados limites considerados. Depois, comparam-se os resultados alcançados através de métodos aproximados com os resultados obtidos através do programa de cálculo automático LUSAS [1], na determinação de cargas críticas e na determinação dos esforços de 2.ª ordem, procurando aqui avaliar algumas considerações presentes no Eurocódigo 3 (EC3) [2], relativamente aos intervalos que obrigam à consideração, ou não, dos efeitos de 2.ª ordem. Por último, apresenta-se a validação da análise dinâmica, finalizando o trabalho com as conclusões finais e os desenvolvimentos futuros.
- Numerical implementation and calibration of a hysteretic model with pinching for the cycling response of steel jointsPublication . Nogueiro, Pedro; Silva, Luís Simões; Bento, Rita; Simões, RuiIn this paper, a hysteretic model with pinching is presented that is able to reproduce realistically the cyclic response of generic steel joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code SeismoStruct is described. The model is subsequently calibrated using a series of experimental test results for steel joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.
- Calibration of model parameters for the cyclic response of end-plate beam-to-column steel-concrete composite jointsPublication . Nogueiro, Pedro; Silva, Luís Simões; Bento, Rita; Simões, RuiComposite joints, considering the composite action of steel and concrete, exhibit, in general, high strength and high ductility. As a consequence, the use of this type of joint has been increasing in many countries, especially in those that are located in earthquake-prone regions. In this paper, a hysteretic model with pinching is presented that is able to reproduce the cyclic response of steel and composite joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code Seismosoft is described. The model is subsequently calibrated using a series of experimental test results for composite joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.
- Typology of seismic motion and seismic engineering designPublication . Mistakidis, E.; Apostolska-Petrusevska, R.; Dubina, D.; Graf, W.; Necevska-Cvetanovska, G.; Nogueiro, Pedro; Pannier, S.; Sickert, J.; Silva, Luís Simões; Stratan, A.; Terzic, U.The paper deals with the influence of the seismic motion typology on the structural response and with engineering design under exceptional actions. Various aspects of seismic motion typology that lead to exceptional actions on the structures are covered. The influence of near fault ground motions, the effect of local site parameters and the magnification of the seismic action on short-period structures are among the parameters identified as dominant for the structural response. The paper presents also a methodology for handling uncertainty in engineering design, based on the mathematical framework of fuzzy analysis. Finally the paper presents various applications of performance based design, which is viewed as a tool as a tool for the analysis of structural behaviour under extreme seismic events. The influence of connection behaviour on the structural response is studied, and applications of the capacity design methodology and of the direct displacement design approach for the evaluation of reinforce concrete structures are presented.
- Influence of joint slippage on the cyclic response of steel framesPublication . Nogueiro, PedroSteel joints subjected to cyclic loading whereby the amplitude of the applied forces exceeds the yield strain of one or more of the relevant connection components usually exhibit degradation of its moment-rotation response that eventually leads to failure of the joint. Depending on the actual design of end-plate beam-to-column steel joints, the cyclic response may present slippage. It is the purpose of the present paper to (i) discuss the various hysteretic models available to model steel joints under cyclic loading; (ii) describe a numerical implementation of two such models, with and without slippage, and (iii) compare the cyclic response of two distinct joints (with and without slippage), and (iv) based on a selected test case, assess the influence of slippage on global behaviour of the structure.
- Numerical implementation and calibration of a hysteretic model with pinching for the cyclic response of steel and composite jointsPublication . Nogueiro, Pedro; Silva, Luís Simões; Bento, Rita; Simões, RuiIn this paper, a hysteretic model with pinching is presented that is able to reproduce the cyclic response of steel and composite joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code Seismosoft is described. The model is subsequently calibrated using a series of experimental test results for steel and composite joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.
- Influence of joint slippage on the seismic response of steel framesPublication . Nogueiro, Pedro; Silva, Luís Simões; Bento, RitaThe present paper presents an evaluation of the influence of joint slippage on the seismic response of steel frames. Using three alternative hysteretic joint models to simulate the connections of a representative low-rise steel frame, and a series of dynamic time-history analyses for a typical seismic record, it is found that slippage affects the response of the structure and should be allowed for in design.
- Residual strength of a steel-concrete composite structure subjected to a design seismic event by firePublication . Nogueiro, Pedro; Santiago, Aldina; Silva, Luís Simões; Bento, Rita; Vila Real, Paulo M.M.This paper presents a numerical investigation of the residual strength of a typical PR momentresistant multi-storey steel framed structure, subjected to a design seismic event followed by fire. In order to allow a calibration with some real results from fire tests on a natural scale, the architectural and structural definitions of the eight-storey steel Cardington building were chosen as the reference case, adapted to deal with basic seismic requirements. The seismic action was simulated with an artificial accelerogram with PGA of 0.6g, chosen to achieve significant energy dissipation in the joints. The adopted fire event is limited to an isolated compartment and it is defined as the natural fire observed during a full-scale fire test carried out at the BRE. Finally, the results are discussed in terms of robustness requirements for extreme events.
- Evaluation of the ductility demand in partial strength steel structures in seismic areas using non-linear static analysisPublication . Nogueiro, Pedro; Bento, Rita; Silva, Luís SimõesThe performance of a structural system can be evaluated resorting to non-linear static analysis, also commonly referred to as Pushover Analysis, because of the nature of application of lateral loads while defining the capacity of the structure. This analysis involves the estimation of the structural strength and deformation demands and the comparison with the available capacities at desired performance levels. This paper aims at evaluating the seismic response of three steel structures using non-linear static analyses, based on the N2 method, adopted by Eurocode 8, the European seismic code. The results are compared with the ones evaluated by means of non-linear dynamic analyses. As a conclusion it can be ascertained that the non-linear static procedures are an alternative tool in seismic assessment and design, over just a force-based design. For structures that vibrate mainly in the fundamental mode, the pushover analysis applied in this work will provide good estimates of global, as well as local inelastic deformation demands.