Frequently Asked Questions (FAQ) About Flat Plate Voided Concrete Slab Systems
The CobiaxUSA voided slab system utilizes hollow, plastic voids made of recycled highdensity, polyethylene (HDPE) that are spaced regularly within the overall thickness of the concrete slab (See Figure 1). The latest innovation is the CLS System (See Figure 2). A voided slab with CobiaxUSA structural formers can be designed and planned by any structural engineer in compliance with ACI 318-19.
Introduction Flat plate voided concrete slab systems, which have been used for many years in Europe and other parts of the world, have become increasingly popular in the U.S. because of the many inherent benefits. Such benefits include reduced weight, which results in smaller seismic forces and larger allowable superimposed loads for given span lengths; economical longer spans without beams; reduced floor-to-floor heights; accelerated construction schedules; and inherent fire resistance that meets the fire-rating requirements in the International Building Code (IBC).
Figure 1 ― CobiaxUSA Slim Line Void formers
Figure 2 – CobiaxUSA CLS Void Formers
The buildings designed with voided slabs have lower floor-to-floor heights, resulting in reduction of building volume, HVAC requirements, façade area, and other vertical elements such as stairs, partitions, piping, and elevator runs. In addition, the thermal mass of concrete buildings helps the cooling and heating cycles as concrete stores and releases the energy to balance the temperature. The energy use of buildings once in service should be considered in the life cycle analysis.
CobiaxUSA routinely receives inquiries concerning various aspects on the design and construction of flat plate voided concrete slab systems. This Technical Note addresses a collection of typical questions, which came from design professionals, including structural engineers, architects, field inspectors, code enforcement officials, and contractors.
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