Consideration of the Torsional Stiffness in Hollow-Core Slabs’ Design

Abstract

The paper discusses the principles of precast concrete hollow-core slabs taking into account their spatial work. It is shown that consideration of spatial work makes it possible to determine the forces in individual floor slabs significantly more precise. The fact that strain redistribution between precast floor slabs depends on slabs’ bending and torsional stiffness is shown. The research has been mostly devoted to determination of the bending stiffness with regard to formation of cracks and the change in torsional stiffness, especially considering the presence of normal cracks, which is still unstudied. This paper presents the technique for determining the torsional stiffness of hollow-core slabs with normal cracks. In order to determine the components included in the resolving system of equations, it is proposed to use an approximation method based on the processing of numerical data using spatial finite elements.

Assessment of the torsional behaviour of hollow core slabs

“…The computational analysis of such a design is normally based on the assumption of the plane stress state. Assuming a plane stress state in the cross-section of the slab is justified when the element is subjected to uniformly distributed loads over its entire surface and when it is supported on two parallel and relatively rigid supports [20,38]. Nonetheless, the response of HC units under torsional actions is much more complex as the cross-section deformations are three-dimensional, presenting secondary bending mechanisms at a cross-sectional level.…”

“…The numerical models developed were able to predict the behavior of the units up to the formation of torsional cracking, but not at higher displacements. Finally, Jurkowska et al [20] presented a technique, based on the processing of numerical data obtained using a finite element (FE) approach, for determining the flexural stiffness of hollow-core units with respect to the formation of cracks and the change in the torsional stiffness.…”