In the last decades, the modernization in structural engineering has increased the use of steel-concrete composite and hybrid systems for slabs, when the adherence in the interface of the materials is present or not, respectively. In addition to the traditional steel deck, a similar solution for precast trussed slabs has been used for small constructions, in which a cold formed U profile acts as steel formwork before the concrete curing, resisting to self-weight of the concrete and to the construction overload. After this period, the steel profile gets incorporated to the concrete element, allowing the composite behavior of the structure, system that usually goes without additional reinforcements. This slab includes, besides concrete, a light filling material between ribs, cold formed profiles and the trussed reinforcement. Once this technology has just arrived to the construction market, there is a gap of knowledge related to its design procedure. In this context, this study aims to present a methodology to analyze the limit-states that govern the design of these slabs. A computational tool was developed to evaluate the resistance through data entry related to geometry, service loads and materials, which grants to conduct a parametric study with pre-defined geometries to obtain, as result, spans and loads. Conclusions about the maximum span without shoring and general data are also discussed. Keywords Steel-concrete composite slabs, trussed slabs, cold formed U profile, design procedure. Evaluation of the resistance of trussed slabs with steel formwork in cold formed U profile Lucas Fadini Favarato et al. Latin American Journal of Solids and Structures, 2019, 16(7 Thematic Section), e178 2/18 (2015) also states that the major advantage in the use of this structural technology is related to the fabrication process: thin plates, with small resistance in its original shape, are stiffened where buckling can occur. Hence, the folding procedure changes steel original mechanical properties, leading to highest yield and ultimate strengths. Otherwise, residual stresses may come up, reducing the ductility of the material. Whereas rolled and welded steel profiles are more suitable for medium and large constructions, cold-formed ones are commonly used in small and medium constructions to compose roof structures, composite slabs and beams, mezzanines, popular houses, small warehouses and up-to-four-storey buildings. In addition, many cross sections are available for design, as C, Z, L and hat, doubled or not, stiffened or not (Silva et al., 2014). One important application of cold formed steel profiles in structural engineering, as presented previously, is in composite slabs. It gets incorporated to concrete after curing, allowing the composite behavior, and works as reinforcement, usually sparing additional ones. Besides, it's necessary to verify the structural safety before concrete curing, in which the steel formwork acts as a single steel beam and must resist to all ultimate limit states that can occur in construction st...

RESUMO Na avaliação de estruturas degradadas é comum a necessidade de se determinarem propriedades mecânicas de estruturas de concreto sem dispor dos dados de projeto. Propriedades como resistência à compressão e módulo de elasticidade, por exemplo, são importantes nessa análise. No entanto, a extração de testemunhos para avaliação laboratorial dos parâmetros de interesse, embora possível do ponto de vista teórico, nem sempre é uma alternativa viável em campo, seja por limitações de tempo, orçamento ou do próprio elemento estrutural. Neste contexto, a opção por ensaios não destrutivos é uma possibilidade que fornece com razoável precisão as informações desejadas. Na literatura, são obtidas formulações matemáticas que correlacionam de forma direta o índice esclerométrico e a velocidade de propagação das ondas ultrassônicas, com resistência à compressão e com módulo de elasticidade. Este trabalho comparou os resultados teóricos com experimentais, por intermédio de ensaios em 26 corpos-de-prova de concretos da Grande Vitória, com diferentes dosagens, tipos de cimento e idades, tendo como parâmetro base a resistência à compressão do concreto. Dessa forma, as conclusões deste estudo apontam para a existência de uma correlação entre os resultados obtidos com os ensaios não destrutivos e os experimentais.

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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.