Análise da influência da altura do edifício no valor do parâmetro 𝜸𝒁 utilizando a inércia equivalente de Branson

Abstract

This work aims to evaluate the influence of building height on the value of the coefficient 𝛾𝑧 using the Branson’s equivalent inertia to consider physical nonlinearity of the beams of in an estimated way, as an alternative the obtaining of this parameter considering the stiffness of the structural elements as recommends the Brazilian Standard code ABNT NBR 6118:2014, reducing it by a single factor and regardless of the height of the building. For this purpose, was adopted as the object of analysis a flat frame of a reinforced concrete residential building where, keeping the same floor type, the frame was analyzed for 9 different heights, being 4 (12 m), 6 (18 m), 8 (24 m), 10 (30 m), 12 (36 m) , 14 (42 m), 16 (48 m), 18 (54 m) and 20 (60 m) floors. The analysis of the frames was held with the Ftool software, considering the reduced inertia of the structural elements according to the referenced standard code in an analysis and in another was adopted for the beams the Branson’s equivalent inertia. Both analyses were conducted to four concrete resistance classes: C30, C45, C60 and C80. From the results of the coefficient 𝛾𝑧 of each frame obtained by two analyses, it was found that the reduction coefficients adopted by the standard code, 𝐼𝑐𝑜𝑙𝑢𝑚𝑛=0,8𝐼𝑐 e 𝐼𝑏𝑒𝑎𝑚=0,4𝐼𝑐, tends to overestimate the values of the coefficient 𝛾𝑧 of porticos and underestimate them in highest frames, compared the analysis considering 𝐼𝑐𝑜𝑙𝑢𝑚𝑛=0,8𝐼𝑐 e 𝐼𝑏𝑒𝑎𝑚=𝐼𝑒,𝑝𝑜𝑛𝑑 according to Branson.