Abstract The use of concrete-filled tubular columns as part of structural systems has steadily increased throughout the years. The growing demand for structural elements of this nature is a direct result of the possibility to use various cross-section shapes that have increased strength, along with resistance to fire and other corrosive agents. The main objective of this article is to present the formulation for optimizing the design of composite columns in accordance with prescriptions from ABNT NBR 16239: 2013, considering financial cost and CO2 emission during manufacturing as objective functions. A Genetic Algorithm was used to solve three examples of composite tubular columns subjected to combined bending and compression, considering major axis and unsymmetrical bending. The financial cost in Brazilian currency and the CO2 emission in kilograms attributed to manufacturing concrete-filled composite columns were calculated and the optimization procedure was implemented on composite columns featuring CHS, RHS and SHS steel members. This study also considers the different concrete strengths and the optional inclusion of longitudinal rebar. For the cases analyzed, the financially and environmentally optimum design corresponds to a CHS composite column with no longitudinal rebar and the highest concrete strength tested, except when unsymmetrical bending is applied, in which case the optimum solution includes longitudinal rebar. Furthermore, results indicate that structural steel has the highest impact on the CO2 emission of the optimal designs. For the column with longitudinal rebar, the reinforcement steel presents the second highest financial impact, while concrete is responsible for the highest influence on CO2 emission.

Resumo Neste artigo, uma análise numérica usando método dos elementos finitos, com apoio do software Ansys, é realizada para avaliar a influência de enrijecedores transversais soldados à alma do perfil de aço na rigidez lateral e no momento fletor resistente de vigas mistas contínuas de aço e concreto à flambagem lateral com distorção (FLD). O modelo numérico desenvolvido foi validado por meio de comparação com os resultados de ensaios realizados por outro pesquisador. Na sequência, foi feita uma análise paramétrica, para vigas com dois e três vãos, variando-se o espaçamento entre os enrijecedores. Finalmente, com base nas análises realizadas, conclui-se que os enrijecedores transversais podem aumentar significativamente a rigidez lateral e o momento resistente de vigas mistas contínuas e um procedimento de cálculo para se obter esse momento, tendo como referência as prescrições da norma brasileira ABNT NBR 8800:2008, é proposto.

Abstract In this paper, a numerical analysis using the finite element method, employing the commercial code Ansys, is performed to evaluate the influence of transverse stiffeners welded to the web of the steel profile on the lateral stiffness and resistant bending moment of continuous steel and concrete composite beams subjected to lateral-torsional buckling (LTB). The developed numerical model was validated by comparison with the results of tests performed by another researcher. Subsequently, a parametric analysis was carried out for beams with two and three spans, varying the spacing between the stiffeners. Finally, based on the analysis performed, it was concluded that the transverse stiffeners can significantly increase the lateral stiffness and the resistant moment of continuous composite beams. A calculation procedure to obtain this moment is proposed, having as reference the prescriptions of the Brazilian standard ABNT NBR 8800:2008.

RESUMO: Este artigo apresenta um procedimento analítico para determinação da resistência de um novo sistema de lajes mistas nervuradas treliçadas, composto por um perfil de aço formado a frio (PFF) do tipo U enrijecido fletido em torno do eixo de menor inércia acoplado a uma treliça eletrossoldada através de conectores plásticos, além de blocos de enchimento e armaduras adicionais. Em decorrência da falta de procedimentos normatizados para esse tipo de sistema, este trabalho combina métodos de dimensionamento de lajes em uma ferramenta computacional capaz de estimar as sobrecargas máximas e escoramento requerido na etapa de construção, base para a tabela de vãos e cargas. Por fim, observou-se forte limitação à construção não escorada pela baixa rigidez do perfil de aço, sendo o sistema capaz de atingir vãos entre escoras de até 1.5 m, em média.

ABSTRACT This paper presents an analytical procedure to determine the resistance of a new composite ribbed lattice slab system, composed by a lipped channel cold-formed steel (CFS) profile in minor bending fastened to a lattice girder by plastic connectors, as well as light filling elements and additional rebar. Motivated by the lack of standardized procedures for such system, this paper combines slab design prescriptions to create a computational tool that estimates load capacity and required propping during construction, serving as a basis for a design catalogue. Finally, a strong limitation of unpropped construction due to the low performance of the cold-formed profile under minor axis bending was observed, being the system able to reach spans up to 1.5 m between props in general.