Assessment of demountable steel-concrete composite flooring systems

Abstract

Sustainability concerns steer the construction sector towards adopting a circular economy philosophy. Steel-concrete composite beams are extensively used in multi-story buildings and bridges due to their competitive construction and efficient material use. Currently the composite action is mainly achieved by headed shear connectors welded to the top flange of the beam, obstructing the non-destructive demountability. Demountable shear connectors can be used in order to open up the composite con-struction for reusability. Demountable shear connectors can take the form of a bolted connection which requires a tight control of construction tolerances. This thesis is fo-cused on studying a bolt coupler connector which is seen as a valuable alternative to the more conventional embedded bolt. The proposed shear connector consists of a bolt and coupler embedded in prefabricated concrete decks which are connected through the top flange of the steel section by an injection bolt.
Full-scale experiments have been performed to investigate the feasibility of construc-tion of a demountable car park. The demountable flooring was obtained by large pre-fabricated concrete decks in combination with tapered beams. Experimental research has confirmed the possibility of assembly and disassembly of the system if construction tolerances are appropriately designed. The most influential factors were quantified based on experimental observations, measurements and finite element models. The hole clearance should be designed keeping in mind the deformability of the system during construction, the manufacturing tolerances and the speed of construction. Experiments show that resin injection can be reliably and labour efficiently used for large oversized holes which allow for higher fabrication imperfections and reduced construction while at the same time enabling composite action of the connectors under live load.
The reusability of the structure was confirmed by a set of eight four-point bending tests considering uniform and non-uniform connector arrangements. Finite element models closely match the experimental results in terms of deflection, stresses and curva-ture. However, the end slip is overpredicted which is in line with research performed by other authors. The efficiency of the non-uniform connector arrangements was studied experimentally and numerically to reduce the construction costs. Concentrating the shear connectors toward the supports will bring the highest benefit in terms of beam bending stiffness without the need of a large number of connectors to prevent uplift.
An extensive cost analysis was performed based on a database of 15500 beam solu-tions generated by a design algorithm develop as part of this thesis. The case study provides a preliminary cost assessment of two demountable steel-concrete composite floorings in order to quantify their economic viability. It was shown that the system constructed with prefabricated solid slabs is more viable compared to the demountable profiled sheeting slab. The most influential contribution to the final cost of the struc-ture comes from the steel work and the labour intensive manufacturing.