Economic viability of demountable steel-concrete composite beams

Abstract

Composite beams are commonly used in current design practice due to their efficient material use and competitive execution. The shear connection is mainly achieved by means of headed studs welded on the top flange. However, the welded connectors obstruct the possibility of a non‐destructive disassembly required to reuse the steel beams and concrete slabs. Raised concern regarding sustainability aspects drive the construction sector to introduce a shear connector which enables the demountability of the flooring. Composite action can be enabled by a bolted connection consisting of an embedded bolt and coupler connected by an external injection bolt through the top flange of the steel beam. This paper aims to assess the initial investment costs and economic viability of two demountable steel‐concrete composite beam solutions. The investigated systems comprise of two different concrete flanges: a prefabricated solid deck and an in‐situ casted profiled sheeting slab. The cost inputs of the analysis were defined by industry experts based on assumed labour and material requirements. The unit price of the novel connector is significantly higher (approx. 15 times) compared to the regular headed welded stud. This justifies the need to optimize the connector arrangement in order to keep the cost per square meter as low as possible. Non‐uniform connector arrangements can be used to reduce construction time and costs with minor decrease in beam stiffness. A tool was developed to generate a batch of 13500 composite beam designs which were later analysed in terms of costs.