Percorrer por autor "Vila-Pouca, Nelson"
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- 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.
- Seismic assessment of a school building in Nepal and analysis of retrofitting solutionsPublication . Rodrigues, Hugo; Furtado, André; Vila-Pouca, Nelson; Varum, Humberto; Barbosa, André R.Recent earthquakes highlighted the vulnerability of some infilled reinforced concrete structures due to the presence and distribution of the infill masonry walls. Buildings such as school buildings and residential buildings are typically not designed considering the contribution of the infill panels to the structure strength and stiffness, when these are subjected to earthquakes. The lack of consideration of the infill panel results in observed poor performance and structural collapses. This manuscript presents a numerical study of a school in Nepal, representative of those existent in the country. Non-linear numerical analyses were carried out to assess the seismic vulnerability in terms of peak inter-storey drifts. In addition, results will be presented and discussed in terms of peak inter-storey drift profiles and peak base shear. Results from a seismic vulnerability assessment of the pre-earthquake structure indicate that the presence of the infill panels in the original structures were responsible for the development a soft-storey mechanism, combined with torsion. Following the seismic vulnerability assessment, four different retrofit solutions were tested and compared with the results of the original structure to gain an understanding on the structural efficiency of each proposed solution. The retrofit solutions proposed revealed to be efficient and reduce the seismic vulnerability. The retrofit solution showing best results correspond to the ones in which reinforced concrete column jacketing was employed.
- Seismic performance of the infill masonry walls and ambient vibration tests after the Ghorka 2015, Nepal earthquakePublication . Varum, Humberto; Furtado, André; Rodrigues, Hugo; Dias-Oliveira, João; Vila-Pouca, Nelson; Arêde, AntónioRecent earthquakes have demonstrated a significant contribution of the masonry infill walls in the structural response of the reinforced concrete (RC) buildings. Field observations after the 25th April’s earthquake in Nepal reinforce the conclusion regarding the influence of the infill walls increasing significantly the structural stiffness, which has a direct impact on the natural frequencies of the structure and of structural elements. Firstly the manuscript focuses on the performance of the infilled RC structures, describing common Nepalese architectural configurations and the major damages observed in infilled RC buildings. Secondly, it shows results from data collected on ambient vibration tests performed in seven infill panels with different characteristics, such as geometric dimensions, openings and levels of damage. These results are used to study the influence of each parameter in the out-of-plane frequency of the wall panels. The present studies along the manuscript are followed by a presentation of the study cases (buildings and the walls), test setups, main results and conclusions.