Analysis of instability of tall buildings with prestressed and waffle slabs

Abstract

The construction system of prestressed flat slabs has been gaining market in Brazil, since it eliminates the use of beams, allows you to perform structures under coluns by area and reduces the cycle of concrete slabs. Thus the analysis of global stability of buildings, takes into account the effects of 2nd order, and these additional effects to the structure obtained from the deformation thereof, calculated by the iterative method P-Delta. The Brazilian ABNT NBR 6118: 2014 [2] assesses the overall stability of reinforced concrete structures through practical parameters, which are the parameter a (Alpha) and gz (Gamma z) coefficient. In this research we seek to study the global stability of slender buildings consist of flat slabs, with slenderness (ratio of the smaller width with the height of the building) approximately one to six, from the modeling of a building with prestressed slabs nonadherent and waffle slabs. To model will use the commercial software CAD / TQS.

Analysis of the global tall buildings stability in flat slabs considering the soil structure interaction

“…After analyzing the results presented here, it can be concluded that the physical nonlinearity coefficients of the elements, the slab transverse stiffness and the discretization of the slab and column meeting area contribute effectively to the reduction of g z and α, as previously verified by Feitosa and Alves (2015) and Passos et al (2016).…”

“…Based on the results of Feitosa and Alves [5] and Passos et al [3], a new model was defined where all the parameters that effectively contributed to the improvement of the g z of the building were used. The MOD0101 model presents the coefficients that simulate the physical nonlinearity (PN) of beams and slabs with values less conservative than those adopted in the reference model MOD0100 and foreseen in ABNT NBR 6118: 2014 [2].…”

“…Recent works on tall buildings for global instability include Passos et al [3], Freitas et al [4] and Feitosa and Alves [5]. In these works the parameter g z is analyzed for different design situations and their influences.…”

“…Important research in the analysis of global stability has been done. Among the most recent works, we can highlight Passos et al [3], Freitas et al [4], Feitosa and Alves [5] and Kimura [6]. However, in these works, the global instability parameter was studied considering only the superstructure, that is, the effect of soil deformations on superstructure displacements was not considered.…”

Statistical analysis of second order effects variation with the stories height of reinforced concrete buildings

“…However, alternatives can also be used, like high stiffness beams, reinforced concrete structural walls, increase of the columns sections in the direction of less rigidity of the structure. Passos et al [13] studied the global stability of slender buildings composed by flat slabs, with slenderness approximately one to six, modeling the building with non-adherent prestressed and waffle slabs. Among factors that enable reductions in the γ z coefficient are: the increase of thickness in prestressed slabs, and the increase of the waffle slabs cover, the reduction of ceiling height between stories in the models and the application of a greater value of the coefficient that considers physical non-linearity in the prestressed slabs.…”