Finite element modelling of hollow core concrete slabs

Cobiax AG is a company who specialises in the design and manufacture of large span concrete flat-slab systems with internal spherical void formers. The internal spherical void formers aim to displace the dead load in the neutral zone of the concrete, hence reducing its dead load. This technology has been used in Europe for over a decade, however the use of Cobiax in Australia remains scarce. This may be due to the fact that Cobiax AG has not provided any scientific data to back up their claims; a serious issue which is addressed in this thesis. This thesis examines the benefits of Cobiax optimised slabs using a finite element (FE) method. Strand7 (2010) FE analysis software and Rhinoceros4 (2010) was used to carry out this study. Solid and Cobiax slabs were modelled in Strand7 and cross-analysed to explore their relative merits. Parameters that were of interest included: the slab's short-term elastic deflections; steel tension stresses; and concrete compressive stresses. The sustainability benefits of using Cobiax were also explored. It was found that Cobiax displayed up to 10% reductions across all parameters explored compared to solid slabs. Further, Cobiax optimised slabs significantly reduced carbon emissions when compared to solid slabs.