Prestressed composite steel-concrete structures are scarcely used due to a lack of clear standardized design guidelines and formulations on the subject. The present research aims to present design methodologies for steel-concrete composite beams with external pretension applied via straight tendons. A computer program to perform structural analysis of such beams was developed based on two different methodologies: the first one is presented in ABNT NBR 8800:2008, in which the guidelines for the design of composite beams with compact webs are adjusted to include the effects of the pretension force. The second methodology is extracted from international literature and presents a structural design process based on stress distribution on the beam. Ninety prestressed and thirty non-prestressed beams were analyzed and designed with the aforementioned computer program to evaluate the influence of beam length, degree of symmetry of the steel profile and eccentricity of the pretension force on the mechanical resistance of the beams. It was observed that, although the prestressing force considerably improved resistance to bending, it introduced high compression stresses on the steel profile; hence, the pre-stressing of composite beams is proved efficient only for steel profiles with symmetrical cross-sections.
O presente trabalho propõe um estudo comparativo do resultado do problema de otimização de blocos de concreto sobre estacas, através do método dos pontos interiores, sendo analisadas as tensões limites nas estacas e no pilar conforme as normas ABNT NBR 6118:2014, ACI (2011), EHE (2008).Além das dimensões dos blocos, seção de aço e da resistência à compressão do concreto, o número de estacas para o projeto final será verificado como variável de projeto no problema de otimização. Exemplos numéricos de blocos de 2 a 6 estacas com os resultados da otimização serão apresentados para demonstrar a aplicabilidade da formulação. Por fim, fez-se uma análise da melhor solução, de modo que o melhor projeto seja escolhido.
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