Design of composite flooring systems for reuse

Composite floor systems are frequently used for high-rise buildings and multi-storey car park buildings, mainly because of the competitive combination of the steel beam and the concrete deck. Traditionally, composite beams are cast in-situ and shear interaction between the concrete and steel beam is provided by welded headed studs. The application of welded headed studs prevents the non-destructive separation of the composite beam, which leads to a very low scoring in the sustainable assessment in terms of the reuse of structural components. An alternative to welded headed studs are bolted shear connectors, which allow for demountability and reusability of a (prefabricated) composite floor system. A key challenge for demountable and reusable composite beams consisting of prefabricated elements is to provide sufficient tolerances to allow for easy execution and demounting, but also to achieve a stiff and strong shear connection under live loads. The required tolerances can, for instance, be obtained by using large bolt-to-hole clearances. The, at first glance, contradictory requirement of a large hole clearance in the execution phase and high stiffness under live loading conditions was solved by using injection bolts. The goal of this paper is to demonstrate how the demountable and composite structures fit in the circular economy framework, and to show that such a demountable and reusable structure was successfully erected and demounted under laboratory conditions. In addition, a cost assessment will be addressed using a simple methodology based on estimated service life (ESL) factors to estimate the annual environmental costs of a composite floor system.