Análise teórica e experimental de lajes nervuradas com nervuras vazadas

Abstract

The waffle slabs are very efficient structures and are constantly evolving being widely used all over the world. The ribbed slab with openings in the ribs is the most recent version of these structures as it further increases the number of advantages of these slabs in relation to solid slabs and even in relation to conventional ribbed slabs. The goal of this research is to develop models to be used in the design of this slab system, using the strut and tie method. The proposed methodology consisted of studying existing models for the design of beams with openings and studying the real behavior of the ribs of slabs with openings in the web to verify the feasibility of using the strut and tie method. Then define appropriate models to verify the elements that compose this structural system, such as flanges, struts, and ties, and then study them through theoretical, numerical and computational analyzes using the finite element method and an experimental program. In the experimental phase, 11 prototypes of slab ribs were tested where it was possible to prove the truss behavior of the concrete ribs. This research presented five significant contributions, mainly due to its originality and innovation character, which comprise: the definition of the behavior of this type of slab, with regard to each of its constituent elements, such as tensioned and compressed chords and diagonals; the definition of an efficiency factor to be used for the diagonal braces in the design phase; the quantification of the topping contribution to the compressive strength of the upper chord, according to the suggested truss model, by defining an effective topping limit width, to be considered in the design phase; the quantification of the shear strength of the mechanisms complementary to that of the truss (Vc), which resulted in calculation models for the shear strength of sections of this type of slab; and the quantification of the contribution of the topping in the shear capacity of the section, which will result in an adequate and efficient calculation model for the shear strength of sections of this type of slab.