Estudo analítico de vigas mistas de aço e concreto com protensão externa
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Data
2021-03-12
Autores
Turini, Thiago Tononi
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Universidade Federal do Espírito Santo
Resumo
Composite steel and concrete beams with external prestressing is an underused structural system in Brazil due in part to the lack of standardization for its calculation. This work aims to propose a methodology for the analysis and design of composite steel and concrete beams supported with external prestressing, considering the effects of prestressing force and using the requirements of ABNT NBR 8800:2008 and ABNT NBR 6118:2014. A computational program was elaborated to automate the calculation of prestressed steel and concrete composite beams according to the proposed methodology, for the cases of pre-tensioning or post-tensioning, in beams constituted by steel profiles of section I doubly symmetrical, solid slabs or mixed steel and concrete and straight or polygonal cables. The proposed calculation methodology was evaluated by comparing the results of the computer program with the experimental results in the last load literature, in prestressed beams submitted to positive and negative moments. In addition, a parametric study with 120 models of prestressed composite beams was performed to analyze the influence, strength and stiffness of these beams, of parameters such as: (i) eccentricity of the prestressing cable, (ii) ratio between span and height of the beam, (iii) height of the concrete slab, (iv) percentage of the maximum prestressing force, (v) type of slab, mixed or massive, (vi) cable layout, straight or polygonal and (vii) prestressing technique, pre-traction or post-traction. The results showed that there is no specific configuration that is the best in all cases and should always analyze what is the critical situation of each project to select the best solution. It was observed that the use of the polygonal tracing presents greater losses of prestressing, in comparison with the straight cable, however it has the advantage of canceling or reducing the negative bending moment in the supports of the structure. For post-tensioned beams, the ratio between the span length and the height of the beam can reach a maximum value between 35 and 40, while for pre-tensioned beams the maximum ratio is between 30 and 35. The height of the slab linearly influences the strength, regardless of the type of slab used. Pre-tensioned beams show better deformation behavior than post-tensioned beams, while in the simplified floor vibration analysis, post-tensioned structures have an advantage.
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Vigas mistas de aço e concreto protendidas , protensão externa , pré-tração e pós-tração , metodologias de análise e dimensionamento