With the advancement technology for reinforced concrete structures, it becomes increasingly feasible to use this technology for steel structures. The objective of this work is to present the formulation of the optimization problem of steel beams with external pretension with straight or polygonal tracing cables, considering the environmental and economic impacts. For the objective function formulation, the minimization of CO2 emission and cost in the design of the structure was considered. As constraints were established the states limits imposed by ABNT NBR 8800:2008. The program was developed within the MATLAB Platform (2016) and the optimization problem solution was obtained through the native Genetic Algorithms method. Routine validation was performed using examples found in the literature and an analysis of the predominant collapse modes was performed. The results indicate that monosymmetric profiles have gains when it comes to reducing CO2 emissions and cost when compared to doubly symmetrical profiles, in addition it was observed that straight cables generate better values of CO2 emission and cost when compared to polygonal cables.

With the advancement technology for reinforced concrete structures, it becomes increasingly feasible to use this technology for steel structures. The objective of this work is to present the formulation of the optimization problem of steel beams with external pretension with straight or polygonal tracing cables, considering the environmental and economic impacts. For the objective function formulation, the minimization of CO2 emission and cost in the design of the structure was considered. As constraints were established the states limits imposed by ABNT NBR 8800:2008. The program was developed within the MATLAB Platform (2016) and the optimization problem solution was obtained through the native Genetic Algorithms method. Routine validation was performed using examples found in the literature and an analysis of the predominant collapse modes was performed. The results indicate that monosymmetric profiles have gains when it comes to reducing CO2 emissions and cost when compared to doubly symmetrical profiles, in addition it was observed that straight cables generate better values of CO2 emission and cost when compared to polygonal cables.

The literature has well established prestressing in concrete beams and its calculation procedures. However, its use in composite steel-concrete beams has increased despite main normative codes lacking a specific approach for it. Designers must, in most cases, combine the available criteria to calculate the standards of steel and reinforced concrete structures. This study aimed to formulate this optimization problem and analyze CO2 emissions for the optimal design of composite steel-concrete beams with external prestressing. The design variables for the optimization problem include cross-section of laminated or welded profiles, slab height, characteristic strength of concrete to compression, and number of tendons. We obtained a solution for the optimization problem via a genetic algorithm (GA) and a particle swarm optimization one (PSO). Comparative analysis with experimental example and with optimization problem of prestressed steel beam are performed. An parametric analysis to several spams is performed, which enabled to evaluate the factors that most impact CO2 emissions. According to results, the chosen algorithms effectively obtained solutions for the problem, and PSO usually provided better results than GA. Regarding the final solution composition, steel contributes the most to emissions, welded profiles provided better solutions than laminated ones, and laminated spans of up to 17.5m and welded ones up to 27.5m dispensed with tendons.

<p>A interação solo-estrutura (ISE) busca analisar a estrutura como uma só, ou seja, sua análise deixa de ser separada para infraestrutura e para superestrutura e passa a ser uma verificação da influência de ambas as partes funcionando simultaneamente. Portanto, este trabalho tem por objetivo analisar e comparar o cálculo de uma edificação com lajes protendidas pelo método tradicional com o cálculo utilizando a ISE em fundações superficiais. Para isso, realizou-se um estudo da melhor distribuição dos cabos na laje de modo a determinar a melhor distribuição quando utilizada a interação solo estrutura. Para a análise, utilizou-se o <em>software</em> CAD/TQS para comparar o parâmetro g_z, o parâmetro de instabilidade a e os deslocamentos horizontais globais das estruturas. De forma a obter uma sensibilidade real no projeto, avaliou-se também uma redistribuição das cargas na fundação nos dois processos. Os resultados dessa comparação mostraram que o emprego da ISE piora os parâmetros de estabilidade, ou seja, deixa de atender os limites impostos pela norma NBR 6118 (ABNT, 2014).</p>