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- Seismic Rehabilitation of RC Columns Under Biaxial Loading: An Experimental CharacterizationPublication . Pinheiro Rodrigues, Hugo Filipe; Arêde, António; Furtado, André; Rocha, PatrícioThe main purpose of this paper is to present an experimental campaign of different strategies for seismic repair and retrofit of RC columns previously subjected to biaxial cyclic loading actions and evaluate the benefits concerning their structural behaviour when again subjected to biaxial cyclic loading. Column rehabilitation was performed in order to improve the ductility and/or strength characteristics and it was obtained through increasing the concrete ductility conditions, with efficient jacketing, or increasing the amount of longitudinal and transversal steel. The aim is, therefore, to contribute in developing and calibrating a procedure that enables the evaluation of the efficiency of different retrofit solutions, their possibilities and fields of application. The results are presented in terms of shear-drift, stiffness degradation, ductility and energy dissipation. The retrofitted results will be compared with the results of the original one, deducting about the structural efficiency by each type of retrofit technique adopted.
- Modal identification of infill masonry walls with different characteristicsPublication . Furtado, André; Pinheiro Rodrigues, Hugo Filipe; Arêde, António; Varum, HumbertoA significant number of structural damages observed in reinforced concrete (RC) structures that occurred in regions affected by earthquakes are due to the presence of the infill masonry walls (IMW). Survey of the structural damages caused by earthquakes reported that the infills panels had an important contri bution in the seismic response of the buildings, namely through the modification of the natural period of the structure due to the increase of the structural lateral stiffness provided. Different failure mecha nisms were observed, in particular the infills’ out-of-plane (OOP) collapse that can have important con sequences for the structure and for the human life’s. The infills’ OOP seismic performance depends on different variables such as the wall geometry, existence of openings, boundary conditions, slenderness and existence of previous damage. This manuscript presents an experimental study of ambient vibration tests on IMW with the main goal of characterize the dynamic properties such as the in-plane and OOP frequencies of the panel and the cor responding vibration modes. For this, two different campaigns were carried out: i) in-situ tests were car ried out in IMW of three infilled RC structures with aim of capture the OOP frequencies and vibration modes of infill panels with different characteristics and evaluate the influence of each variable; ii) labo ratory tests were carried out on a full-scale infilled RC frame in order to evaluate the natural frequencies evolution along the period after construction. Additionally, it was evaluated the effect of the axial load in the adjacent RC columns and also the existence of damage on the IMW natural frequencies and corre sponding vibration modes. From the results, it was observed that the openings reduced the OOP frequen cies around 20–40%, the axial load increment in the adjacent columns increased the OOP stiffness and consequently the natural frequencies of the panel.
- Numerical modelling of RC strengthened columns under biaxial loadingPublication . Rodrigues, Hugo; Furtado, André; Arêde, António; Varum, HumbertoDuring an earthquake, the reinforced concrete (RC) structures are subjected to deformations that may lead their structural elements to exceed the corresponding resistance limit state, forcing them to have nonlinear responses. The application of realistic numerical models that can represent the non-linearity of each structural element requires full examination and calibration. Furthermore, simplified numerical approaches that can represent the seismic behaviour of original and strengthened RC elements are of full importance. For this, the experimental tests are useful to calibrate the numerical models, and thus to capture as well as possible the real response of the elements. The main goal of this work is to evaluate the efficiency of a simplified numerical approach to represent strengthened RC columns with steel and CFRP jacketing, subjected to biaxial horizontal loading. The numerical modelling efficiency will be evaluated by comparing the numerical results with the experimental ones in terms of shear-drift hysteretic behaviour, initial stiffness and stiffness degradation, maximum strength and energy dissipation. The results shows a good performance of the numerical models, mainly for the RC columns strengthened with CFRP jacketing technique.
- Mainshock-aftershock damage assessment of infilled RC structuresPublication . Furtado, André; Rodrigues, Hugo; Varum, Humberto; Arêde, AntónioThe primary objective of this manuscript is to present a numerical study regarding the mainshock-aftershock damage assessment of infilled reinforced concrete (RC) structures. For this, an 8 storey building was built in the OpenSees software considering different modelling strategies: (i) RC structure without infill masonry walls; (ii) RC structure with infill walls considering only the in-plane behaviour; and (iii) RC structure with infill walls considering the combined in-plane and out-of-plane non-linear behaviour. Two different approaches are proposed to assess the seismic vulnerability of undamaged and damaged structures due to mainshock-aftershock sequences. Both methodologies are described throughout the manuscript. Incremental dynamic analysis were carried out to achieve fragility curves for different damage states of the structures. A comparison between the undamaged and damaged structures’ fragility curves will be presented and discussed which will allow to assess the effect of the mainshock-aftershock. Furthermore, the effect of the infill walls presence and the consideration of the combined in -plane and out-of-plane behaviour will be discussed.
- Out-of-plane behavior of masonry infilled RC frames based on the experimental tests available: a systematic reviewPublication . Furtado, André; Rodrigues, Hugo; Arêde, António; Varum, HumbertoThe primary objective of this manuscript is to present a systematic review of experimental studies regarding infill masonry walls out-of-plane (OOP) behaviour. An extended database was built containing information from each experimental campaign and specimen tested. Parameters such as geometric dimensions, material and mechanical properties, test setups and loading protocols and test results were collected. A systematic review methodology s conducted with the aim of filter the more relevant work in this field. For the analysis of each parameter in the infill wall OOP performance, three different groups were defined: as built specimens, specimens with previous in-plane damage and retrofitted specimens. Comparisons were drawn between the specimens of each group to assess the impact of those parameters on the panel response. Empirical relationships were proposed to predict the infill panels OOP capacity according to the aspect ratio, panel slenderness, percentage of masonry units’ voids, masonry properties and previous in-plane drift. The results demonstrated that previous damage caused by in-plane tests that reached a maximum drift until 1.25% can reduce about 70% the OOP capacity of the panel, changing the failure mode of the panel that can result in fragile collapses. It was also observed that the parallel flexural strength parallel to the horizontal bed joints can increase the panel OOP maximum strength until 5 times.
- Seismic precast. Seismic performance assessment of existing precast industrial buildingsPublication . Furtado, André; Arêde, António; Rodrigues, Fernanda; Rodrigues, Hugo; Vitorino, Hugo; Varum, Humberto; Ostetto, Liana; Batalha, Nádia; Fernandes, Paulo; Sousa, Romain; Silva, VítorPast seismic events exposed important fragilities in precast reinforced concrete buildings and highlight the need to undertake measures to mitigate future losses.The study presented identify potential structural and nonstructural fragilities of the Portuguese building stock and provide guidance to reduce the associated direct and indirect socio-economic impact
- Load-path influence in the response of RC buildings subjected to biaxial horizontal loadings: numerical studyPublication . Furtado, André; Rodrigues, Hugo; Arêde, AntónioThe study of the reinforced concrete (RC) columns’ response to horizontal loads is of full importance to understand how earthquakes affect the integrity of structures, essentially those already built and especially vulnerable to this type of action, as is the case with many existing buildings on significant seismic activity zones which are not adequately prepared for that eventuality. Consequently, there is also the need to perform a significant number of experimental and numerical studies to understand how much the columns resistance is affected by the horizontal loading path combined with axial load. The present study focus on the comparison between the RC columns response when subjected to uniaxial and biaxial loading through a literature review of the experimental test data results. Additionally, a parametric study was performed to analyze the load-path influence in the columns response. Non-linear static pushover analysis were performed in more than 36 columns with different cross-sections, reinforcement ratios and axial load ratio, performing a total of 1300 analysis. The numerical results will be presented in terms of capacity curves, maximum strength comparison between the uniaxial and the biaxial response and several ratios were also determined to a do a better comparison.
- 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.
- Experimental study of repaired RC columns subjected to uniaxial and biaxial horizontal loading and variable axial load with longitudinal reinforcement welded steel bars solutionsPublication . Rodrigues, Hugo; Furtado, André; Arêde, António; Vila-Pouca, Nelson; Varum, HumbertoThe study of the reinforced concrete (RC) columns’ response to horizontal cyclic loads is of full importance to understand how earthquakes affect the integrity of structures. Essentially those already built and especially vulnerable to this type of action, as is the case of many existing buildings on significant seismic activity zones which are not adequately prepared for that eventuality. Consequently, there is also the need to perform a significant number of studies of repairing procedures of structural elements, so as to restore its function and possibly achieve an improvement in relation to its original seismic resistance. The present experimental work is focused in the study of welding joints for steel bars used in building columns, supported by tensile tests on specimens according to the actual welding regulations. The experimental results are analyzed and discussed with particular attention to the specimens’ behaviour in terms of strength and ductility compared to the results obtained for original steel bars. After the definition of the proper welding solution, six RC columns previously tested were repaired and retrofitted with this solution tested under uniaxial and biaxial horizontal loading and variable axial load in order to compare the global result with the original tested columns and the effects introduced by the repair process.
- Prediction of the earthquake response of a three-storey infilled RC structurePublication . Furtado, André; Rodrigues, Hugo; Arêde, António; Varum, Humberto; Grubišić, Marin; Šipoš, Tanja KalmanOver the last years, the seismic behaviour of infilled reinforced concrete (RC) structures has been the focus of innumerable experimental and numerical studies. A big effort is being made by the scientific community to increase the knowledge regarding the seismic performance of these types of structures and to improve the numerical modelling capabilities to predict their expected behaviour accurately. In 2015, a blind prediction contest was organized by the Faculty of Civil Engineering, University of Osijek, with the main goal of inviting the technical and scientific community to predict the nonlinear seismic behaviour of a 1:2.5 scaled 3D building structure. A three-storey infilled RC structure was subjected to a sequence of ten incremental earthquakes in a shake table test. The blind numerical simulations were carried out by different international teams invited by the organizational committee. The teams knew only the specimen geometry, reinforcement detailing, material properties, and ground motions recorded during the testing. In this context and, in the light of the authors’ success in the contest, the present paper mainly aims at presenting several issues regarding the numerical modelling strategies adopted (and related difficulties) which proved to yield good results while also providing some insight regarding key problems in numerical simulations of infilled RC structures under seismic actions. The main numerical results obtained by all of the participating teams will be presented and compared with the experimental ones. Discussion concerning the reasons behind the mismatching of some results will be presented. Finally, a parametric study was carried out with the aim of assessing the influence of some modelling issues and parameters on the structural global response, in particular when affected by some variations.