A low-carbon deconstructable steel-concrete composite framed system with recyclable beam and slab components

As attention is being focused increasingly towards minimising carbon emissions and enhancing the possibly of material recycling in the construction industry, conventional composite floor systems are problematic for many reasons. In this research, it is proposed that precast concrete slabs can be attached to a steel frame with semi-rigid bolted connections using Post-installed Friction-grip Bolted Shear Connectors (PFBSCs). Moreover, the use of geopolymer or low-carbon concrete in the casting of the slabs eliminates the use of ordinary Portland cement. The investigation in this research is divided into experimental and theoretical studies. The experimental program comprises of five different series of tests. In the first series, push-out tests are conducted to determine the load-slip behaviour of PFBSCs. In the second to fourth series, twelve full-scale end plate beam-to-column joints are tested. All joint specimens are designed to simulate the behaviour of an internal joint in a semi-rigid frame. The fifth series is conducted on four full-scale composite beams. In all specimens, composite action between the steel girders and concrete slabs is provided by PFBSCs. ABAQUS software is used to develop 3D finite element models of the composite beams and joints investigated, and is shown to accurately simulate their observed structural behaviour. A parametric study is performed using the calibrated models to investigate the influence of different parameters on the structural behaviour of deconstructable composite joints with PFBSCs. Simple models are also proposed, which demonstrate the influence of the main parameters. Both the joints and beams demonstrate very significant ductility, with large rotations, deformations and interface slips being developed and sustained during the testing. In addition, the pre-tension induced in the bolts provides sufficient frictional resistance between the precast slabs and steel beams to ensure that the composite system has full shear interaction throughout the range of service loading. It is also confirmed that composite beams and joints with PFBSCs can be deconstructed easily at the end of their service life, with the slabs, steel beams and bolts being reusable in other structural applications. This study shows that the innovative composite framed system proposed herein is an ideal alternative for traditional composite system