Rupture mechanisms in the experimental analysis of prestressed hollow core slabs considering height variation

ABSTRACT

The first’s hollow-core slabs were produced by 1950 in Finland and had circular cross section of 150, 200 or 265 mm height. By 80’s, non-circular hollow core slabs became popular in 320, 370, 400 and 500 mm height. This work is a continuity of precast floors studies done by Núcleo de Estudo e Tecnologia em Pré-moldados de Concreto (NETPre), and aims to analyze the rupture mechanisms of prestressed hollow core slabs subjected to shear tension with an emphasis on comparative study in variation of height in slabs (high and low height slabs). In this work, destructive tests carried out according to EN1168 were analyzed in 06 slab prototypes (3 with 200 mm height and 3 with 300 mm height) with 6 m length each, with the application of a concentrated load until the rupture for evaluation of resistance to ultimate shear force. From the analysis of the resistant mechanisms it was concluded that 200 mm slabs presented greater influence of flexural mechanism which resulted in a larger deformability of the element for lower values of applied force in comparison with the higher slabs. In the case of 300 mm slabs, the rupture mechanism of shear tension was defined as sudden rupture and the appearance of a typical inclined crack with extension from the support to the point of application of the load. In addition, with the behavior and results that slabs showed near the ruin point, it can be concluded that both 300 mm and 200 mm slabs presented good anchoring efficiency. The slipping of the strings occurred only after the shear rupture in flexural-fissured region according to the calculation criteria adopted in NBR14861.

Keywords
Hollow-core slab; Shear tension; Rupture mechanism