Preliminary Research Towards A Semi-Prefabricated LVL– Concrete Composite Floor System for the Australasian Market

Abstract

The choice of the best floor solution has always been a key issue in the design and construction of multi-storey timber buildings. Strict performance requirements such as effective acoustic separation of inter-tenancy floors, thermal mass, fi re resistance, limitation of deflection, resistance to vibrations and effective diaphragm action are very hard to comply with if only timber is used. The main purpose of this paper is to present the preliminary and some ongoing research in the short- and long-term carried out ainly at the University of Canterbury, New Zealand, for the realisation of a semi-prefabricated laminated veneer lumber (LVL)-concrete composite floor system in both the local and Australasian market. The paper discusses a novel semi-prefabricated LVL-concrete composite system where panels made from LVL joists and plywood flooring are prefabricated off-site. Once the panels are lifted onto the supports and connected side-by-side, a concrete topping is cast-insitu so as to form a continuous slab connecting all the panels. Composite action between the concrete topping and the panels is achieved using different types of connectors, such as various forms of notches cut from the LVL joists and reinforced with coach screws or toothed metal plates pressed in the LVL joists. After pointing out the advantages of the proposed system over traditional only-timber and only-concrete floor solutions, the paper describes push-out tests in the short-term on connections used in the LVL-concrete composite. Tests to failure of small LVL-concrete composite blocks (push-out tests) with different types and shapes of connection systems were performed at the University of Canterbury, New Zealand, and at the University of Technology Sydney, Australia. The results are parametrically evaluated and discussed in detail. The failure mechanism of the notched connection is highlighted together with the strength and stiffness values for each tested connection system. Subsequently, the four best connection systems were identified and used in beam specimens of 8–10 m in span. The experimental program on the beams is presented briefly in order to provide information of the different phases of the project.