Innovative demountable steel-timber composite (STC) beams: Experimental full-scale bending tests

This study introduces an innovative demountable steel-timber composite (STC) flooring system with potential for reuse. The flooring system consists of downstanding hot-rolled I-shaped steel profiles and laminated veneer lumber (LVL) slabs connected to the steel beams with novel shear connectors. This STC flooring system aimed at reducing embodied carbon and optimizing the use of resources, offer an alternative to traditional, carbon-intensive flooring systems. The novel shear connections implemented in the STC beams facilitate demountability, adaptability, reconfiguration, and relocation of structural components, aligning with circular economy principles. Moreover, this flooring system exhibits significant promise for modularization, standardization, and off-site serial production, making it ideal for prefabrication in standard sizes and modules. Two full-scale STC beams, each with a span of 10 m, an LVL slab width of 2.51 m and thickness of 144 mm connected to a steel profile IPE 400, were simply supported and tested in six-point bending to assess their flexural response. The two tested beams were identical in terms of geometry, materials, and shear connection distribution, but differed in the type of shear connection implemented. This contribution outlines the details of the innovative flooring system and the novel connections that enable demountability and reusability of the components. Specifics of the two STC beam specimens, their assembly, the test setup, the instrumentation, and the testing procedure are presented. The results of the two full-scale bending tests demonstrate their significant load-bearing and deformation capabilities as well as potential for reuse. Additionally, the results indicate the efficacy of the novel shear connections and the beams' overall structural integrity. Despite the extensive deformation of the STC beams, the shear connections remained undamaged and slip values of less than 7 mm were recorded in the last loading stages. Within the elastic range, maximum slip values of less than 1 mm were recorded, highlighting the structural components' potential for reuse. Midspan deflections exceeding l/20 demonstrate good ductility. Strain measurements on the timber slabs revealed that the slabs' width was not fully utilized, leading to the determination of an effective width of l/5.5.