Structural performance of ventilated ground slabs using IGLU' modules

Abstract

IGLU' modules are innovative and efficient building units for creating under-floor cavities in ground slabs. Under-floor natural or forced ventilation ensures elimination of humidity present in the cavity. The research focused on the performance of three distinct IGLU' modules having different heights and shapes on which their manufacturer Daliform s.r.l. Italy does not have any information. Such a system is already used in Malta but it had not yet been backed up by research. This research should help the designer to obtain basic information on the load carrying capacities and failure modes of such system but further research should be held in light of the CE Marking in the near future. As part of this research, parametric studies were carried out. The tests undertaken are not conclusive because the number of samples tested is small in comparison to the variables involved. The constant parameters were: the concrete sub-base, the concrete grade, the loading position, the loaded area and the amount of reinforcement. The variable parameters included: three different IGLU' module heights having different shapes, reinforcement type, topping height and two different loading scenarios. From the investigations carried out in this study the following conclusions can be drawn: • Increasing concrete topping increases the stiffness of the slab irrespective of module height and shape. Punching failure is a critical failure mode in such system while flexural failure determined thicker slabs. 11 Modules having a circular geometric structure (160mm high) proved to have a higher loadcarrying capacity than those having a flat geometrical structure (120mm high), while 40mm modules having shorter support spacing proved to be stiffer and failed by crushing of the supports. • Though steel fibres improve the flexural toughness of the concrete, it was observed that steel fibre reinforced slabs have a lower load-carrying capacity than welded wire fabric reinforced specimens. It was also observed that the addition of steel fibres increased the residual strength of the specimens. • The tests show that ventilated ground slabs using IGLU' modules need greater attention for the control of settlement than a standard ground slab. • Test results show that they are in conformity with other test results presented by Daliform and Grima (2005)

The cost factor is important to determine whether it is economical to opt for this type of construction instead of the standard traditional construction technique. This system is not as cost effective as one would like it to be, hence inhibiting its potential use in the industry. However, performance advantages of ventilated ground slabs are considered as long term benefits. In spite of the fact that these advantages cannot be directly evaluated, they should still be taken into account. It is then up to the owner and/or specifier to decide what performance is desired and at what price.