Automatização do cálculo de vigas mistas de aço e concreto com lajes alveolares pré-moldadas
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Data
2025-03-31
Autores
Rocha, Jonas da
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Universidade Federal do Espírito Santo
Resumo
The study of technologies aimed at better utilization and optimization of materials to make projects more economical, sustainable, and faster to execute is of utmost importance. Projects that use composite beams with precast hollow-core concrete slabs are scarce, partly due to a lack of knowledge about the system and its design methods. However, in 2024, the ABNT NBR 8800 standard was updated to include normative prescriptions and the design methodology for composite beams with precast hollow-core concrete slabs, which served as the basis for this work. A computational program was developed to automate the analysis and design calculations of steel composite beams with precast hollow-core concrete slabs, following the proposed methodology for internal and edge composite beams composed of doubly symmetric I-sections and precast hollow-core slabs. The procedures were outlined in design flowcharts and later implemented in the program, which was developed using VBA (Visual Basic for Applications). The program selects the lightest rolled or welded I-section that meets the acting demands, providing a calculation report at the end with the main design information. The computational tool was validated through a comparison with an adapted example from the Gerdau composite beams with hollow-core slabs manual (Queiroz, Rocha, and Filho, 2017), which, along with NBR 8800:2024, served as a foundation for the methodology presented here. Furthermore, a parametric study with 72 composite beam models with hollow-core slabs was conducted to analyze the ultimate limit states (ULS) governing the design of this type of structure, as well as the influence of the concrete topping thickness and the characteristic compressive strength of concrete (𝑓𝑐𝑘) on beam strength. The results showed that the design was governed by the balanced phase, where the applied moment is generated by the support of two hollow-core panels on the top flange of the steel section in cases of shorter beam and slab spans, and by the composite phase in cases of longer beam and slab spans. Additionally, the increase in beam strength with higher 𝑓𝑐𝑘 values was significant when a compact-web profile was used but irrelevant when a semi-compact-web profile was adopted. The serviceability limit state (SLS) was not considered critical, mainly because cambering was applied whenever necessary. This work also enabled the development of preliminary design tables for composite beams with hollow-core slabs, providing a useful tool for professionals in the early stages of design. The tables present the steel profiles and the maximum superimposed loads (𝑞𝑠𝑐) for full interaction, according to the span of the beam and the slab.
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Lajes alveolares pré-moldadas , Metodologia de dimensionamento , Programa computacional