Browsing by Author "Varum, Humberto"
Now showing 1 - 10 of 36
Results Per Page
Sort Options
- Comparative structural response of two steel bridges constructed 100 years apartPublication . Varum, Humberto; Sousa, Romain; Delgado, Walter; Fernandes, Catarina; Costa, Aníbal; Jara, José; Jara, Manuel; Álvarez, JesúsThis paper presents a comparative numerical analysis of the structural behaviour and seismic performance of two existing steel bridges, the Infiernillo II Bridge and the Pinhão Bridge, one located in Mexico and the other located in Portugal. The two bridges have similar general geometrical characteristics, but their construction is separated by one hundred years. 3D structural models of both bridges were developed and analyzed for various load cases and several seismic conditions. The results of the comparative analysis between the two bridges are presented in terms of natural frequencies and corresponding vibration modes, maximum stresses in the structural elements and maximum displacements. The study aimed at determining the influence of one century period in material properties, transverse sections and expected behaviour of two quite similar bridges. In addition, the influence of the bearing conditions in the global response of the Pinhão Bridge was evaluated.
- Comparative study on the seismic performance assessment of existing buildings with and without retrofit strategiePublication . Rakesh, Dumaru; Rodrigues, Hugo; Varum, HumbertoA large number of inflled RC frame buildings have undergone moderate to extensive structural damages and even collapsed after the 2015 Gorkha earthquake. The repair and maintenance works are still being carried out in the existing RC buildings, many of them without any consultation with design engineers. Such practices are likely to create a beneft of doubt on the efciency of the retroftting works and repair/maintenance works. Therefore, the present study aims to evaluate the seismic performance of the existing non- and pre-engineered buildings, and later employed retroft measures that are commonly practised in the region. The analytical results revealed that the selected buildings were seismically defcient and are most likely to undergo extensive damage to collapse states, at 0.3 g PGA. It was found that the retroft measure signifcantly enhances the stifness, maximum strength and ductility in the existing buildings. The pushover curves indicated that the steel bracing highly increased the stifness, strength and ductility capacity in all case study buildings. The steel-braced building was recorded to have increased the maximum base shear capacity by almost ten times for the soft-storey MRT1 building. Similarly, the retroft measures also eliminated the potential single storey drift concentration recorded in the original building, such that a uniform inter-storey drift profle can be attained throughout. The conditional probability of collapse for the case study buildings, at 0.3 g PGA, ranges from 13.5 to 42% and could be minimized below 4% in the worst case scenario for the shear wall. All the numerical results demonstrated that steel bracing was much more efective in enhancing the seismic performance of the existing buildings.
- Comportamento Sísmico de um Pavilhão Pré-Fabricado de Betão ArmadoPublication . Batalha, Nádia; Rodrigues, Hugo; Varum, Humberto; A. L. Fernandes, Paulo; Sousa, RomainOs pavilhões pré-fabricados de betão armado são muito comuns no parque industrial em Portugal, tendo mostrado um desempenho por vezes deficiente em sismos recentes tanto ao nível dos elementos estruturais como não-estruturais. Torna-se importante a sua caraterização a fim de conhecer melhor o seu comportamento sísmico. Os pavilhões industriais de um piso, com uma estrutura porticada de vigas e pilares, com ligação encastrada na base e rotulada no topo, sobre a qual vigas de secção variável são posteriormente apoiadas é a solução mais recorrente em Portugal. Nesse sentido, este trabalho aborda o comportamento sísmico de um pórtico de um edifício industrial-tipo existente, com estrutura em betão pré‐fabricado. Essa caracterização é feita através de análises estáticas não lineares (pushover) e análises dinâmicas. Os resultados obtidos são apresentados e discutidos.
- Cost-benefit analysis of retrofitted non-engineered and engineered buildings in Nepal using probabilistic approachPublication . Dumaru, Rakesh; Rodrigues, Hugo; Varum, HumbertoThe applicability and suitability of the retrofit techniques adopted to enhance the seismic performance of the existing pre-engineered and non-engineered buildings were investigated through probabilistic cost-benefit analysis. The primary objective of the study aims to support, motivate, and encourage the decision makers, owners, investors, and concerned stakeholders to invest money for retrofitting of existing seismic deficient buildings. The study also aims to identify the best retrofit technique through the comparison of cost-benefit ratio. For this, the study investigates four existing buildings, representing two buildings for each non-engineered and pre-engineered design approaches. The selected non-engineered buildings were built in late 90's and pre-engineered buildings between late 90's to 2015. After rigorous analysis, it was revealed that the unexpected losses (in terms of monetary values) could be minimized by large extents, i.e. (2-11) times for non-engineered and (3-50) times for engineered buildings with the intervention of retrofit strategies. The attained expected annual loss for as-built and retrofit buildings evaluated through discrete distribution as a function of two intensity measures reveals that the maximum expected annual loss ensues between 0.1g and 0.2 g PGA for non-engineered buildings and below 0.1 g PGA for pre-engineered buildings. A higher cost-benefit ratio value can be attained if the service life of the building structure is increased or decreased discount rate. For most of the studied buildings, buildings retrofitted with RC shear wall found to be the most economically viable, and followed by steel bracing and jacketing, respectively.
- Double-Leaf Infill Masonry Walls Cyclic In-Plane Behaviour: Experimental and Numerical InvestigationPublication . Furtado, André; Rodrigues, Hugo; Arêde, António; Varum, HumbertoBackground: The infill masonry walls are widely used in the construction of reinforced concrete buildings for different reasons (partition, thermal and acoustic demands). Since the ‘60s decade, one of the most common typology in the southern Europe was the double-leaf infill walls. Recent earthquake events proved that this specific typology have an important role in the seismic response of reinforced concrete structures in terms of stiffness, strength and failure mechanisms. However, modelling approaches of these specific infill panels cannot be found over the literature. Objective: Due to this, the major goal of the present manuscript is to present a simplified modelling strategy to simulate the double-leaf infill masonry walls seismic behaviour in the software OpenSees. Method: For this, two different modelling strategies were proposed, namely through a global and an individual modelling of the panels. An equivalent double-strut model was assumed and both strategies were compared and calibrated with experimental results from a full-scale in-plane test of a double-leaf infill masonry wall. Results: The numerical results obtained by each strategy are very accurate in terms of prediction of the specimen’ initial stiffness, maximum strength and strength degradation. Conclusion: From the force evolution throughout the tests, it was observed differences lower than 10%. Globally, the individual modelling approach reached better results.
- Earthquake loss estimation for the Kathmandu ValleyPublication . Chaulagain, Hemchandra; Rodrigues, Hugo; Silva, Vitor; Spacone, Enrico; Varum, HumbertoKathmandu Valley is geologically located on lacustrine sediment basin, characterized by a long history of destructive earthquakes. The past events resulted in large structural damage, loss of human life’s and property, and interrupted the social development. In recent years, the earthquake risk in this area has significantly increased due to uncontrolled development, poor construction practices with no earthquake safety provisions, and lack of awareness amongst the general public and government authorities. In this context, this study explores the realistic situation of earthquake losses due to future earthquakes in Kathmandu Valley. To this end, three municipalities: (a) Kathmandu Metropolitan City, (b) Lalitpur Sub-Metropolitan City and (c) Bhaktapur Municipality are selected for a case study. The earthquake loss estimation in the selected municipalities is performed through the combination of seismic hazard, structural vulnerability, and exposure data. Regarding the seismic input, various earthquakes scenario considering four seismic sources in Nepal are adopted. For what concerns the exposure, existing literature describing the construction typologies and data from the recent national census survey of 2011 are employed to estimate ward level distribution of buildings. The economic losses due to the earthquake scenarios are determined using fragility functions. Finally, the ward level distribution of building damage and the corresponding economic losses for each earthquake scenario is obtained using the OpenQuake-engine. The distribution of building damage within the Kathmandu Valley is currently being employed in the development of a shelter model for the region, involving various local authorities and decision makers.
- Effect of the panel width support and columns axial load on the infill masonry walls out-of-plane behaviorPublication . Furtado, André; Rodrigues, Hugo; Arêde, António; Varum, HumbertoThe aim of this research is to contribute to increase the understanding regarding the infill panels’ OOP behavior and evaluate the influence of different variables in the panel’ performance, such as: gravity load and panel support condition. For these experimental tests were carried composed by two full-scale infill panels subjected to uniform OOP pressure applied by airbags, subjected to gravity load applied in the top of the frame ‘columns and the other one was built partially supported in the bottom beam. The second goal of this work was to perform a comparative study between these two specimens with other three tests already tested.
- Estudo da eficiência de diferentes técnicas de reforço em edifícios de betão armado com r/c vazadoPublication . Furtado, André; Rodrigues, Hugo; Varum, Humberto; Costa, AníbalA avaliação e o reforço de edifícios existentes de betão armado, por forma garantir a sua segurança face a uma dada ação sísmica, é um tópico de elevada importância e premência, tal como comprovado nos recentes sismos ocorridos por todo mundo, e particularmente em países do sul da Europa. Assim, reconhece-se que deve dar-se atenção à investigação na área da análise e reforço das construções existentes. Algumas soluções arquitetónicas adotadas até aos anos 70, combinadas com a prática naquele período do projeto estrutural, particularmente no simplificado ou inexistente cálculo sísmico, fizeram com que muitas dessas estruturas tenham associada uma vulnerabilidade elevada, podendo sofrer danos consideráveis se solicitadas por um sismo. O objetivo principal deste trabalho é o estudo da eficiência de diferentes técnicas de reforço aplicadas a um edifício existente de betão armado com paredes de alvenaria de enchimento com comportamento potencialmente condicionado pelo mecanismo tipo soft-storey. Numa primeira fase foi também analisada a influência, já comprovada em trabalhos anteriores, da presença dos painéis de alvenaria de enchimento na resposta dos edifícios face a uma ação sísmica, sendo avaliado de seguida a sua vulnerabilidade sísmica. Após avaliada a sua vulnerabilidade foram adotadas no modelo numérico diferentes técnicas de reforço, nomeadamente: o encamisamento de pilares recorrendo ao betão armado, a adição de paredes resistentes de betão armado, a introdução de contraventamentos metálicos com e sem elementos dissipadores de energia. Os resultados das análises da resposta do edifício reforçado com as várias técnicas são confrontados com os respetivos resultados da estrutura original, deduzindo-se sobre a melhoria do desempenho estrutural com cada tipo de reforço estudado.
- Evaluation of Analytical Methodologies to Derive Vulnerability FunctionsPublication . Silva, Vitor; Varum, Humberto; Crowley, Helen; Sousa, Romain; Pinho, RuiThe recognition of fragility functions as a fundamental tool in seismic risk assessment has led to the development of more and more complex and elaborate procedures for their computation. Although vulnerability functions have been traditionally produced using observed damage and loss data, more recent studies propose the employment of analytical methodologies as a way to overcome the frequent lack of post-earthquake data. The variation of the structural modelling approaches on the estimation of building capacity has been the target of many studies in the past, however, its influence in the resulting vulnerability model, impact in loss estimations or propagation of the uncertainty to the seismic risk calculations has so far been the object of restricted scrutiny. Hence, in this paper, an extensive study of static and dynamic procedures for estimating the nonlinear response of buildings has been carried out in order to evaluate the impact of the chosen methodology on the resulting vulnerability and risk outputs. Moreover, the computational effort and numerical stability provided by each approach were evaluated and conclusions were obtained regarding which one offers the optimal balance between accuracy and complexity.
- Evaluation of different strengthening techniques’ efficiency for a soft storey buildingPublication . Furtado, André; Rodrigues, Hugo; Varum, Humberto; Costa, AníbalThe assessment of seismic vulnerability and strengthening of existing buildings is a topic of relevant importance and priority, as evidenced in recent earthquakes around the world, particularly in Southern European countries. Some architectural solutions adopted in the decade of 1970, combined with the common design and construction practices at that time, particularly in what regards to the seismic design, influences the seismic vulnerability of these structures. The objective of the present work is to study, based on numerical analyses, different strengthening techniques to adopt into an existing building with the behaviour potentially governed by soft storey mechanism when subjected to seismic actions. The influence of the masonry infill panels will be studied and the seismic safety of the building will be assessed. Also, different strengthening techniques will be tested to fix/eliminate the soft storey like response, namely: RC columns jacketing, addition of steel bracings with and without shear link and addition of RC shear walls. The strengthened buildings results will be compared with the results of the original structure, deducting about the structural efficiency by each type of strengthening technique adopted. The costs associated to each solution will be determined and compared with the market value of the building.