On the load‐carrying behaviour of CSTC slim‐floor beams

Composite steel truss and concrete (CSTC) beams are steel‐concrete composite structures mostly used as slim‐floor systems in industrial buildings. The proposed paper focuses on the load‐bearing behaviour of the so called NPS beam system as a specific type of CSTC beam. This system is made of a sinusoidal smooth steel truss welded to a steel plate, and embedded in cast‐in‐situ concrete. Unlike standard composite beams, NPS beams do not have dedicated shear connectors for transferring the longitudinal shear force from the steel part to the concrete. The shear connection between steel and concrete is enabled by the sinusoidal bar as an integrated part of the steel profile. The load‐slip behaviour of the shear connections in NPS beams was recently investigated through push‐out tests and appropriate design rules were proposed to predict their resistance. However, the longitudinal shear connection behaviour within the overall beam system is still not fully understood and requires further investigations. Furthermore, the ductility of composite slim floor systems depends strongly on their geometrical and mechanical properties. Strain‐limited analyses provide more reliable design predictions, but typically still simplify the shear connection behaviour strongly. It is therefore reasonable to conduct full‐scale experimental tests to investigate the structural behaviour at a cross‐sectional and a global level. The presented work addresses those issues through preliminary strain‐limited analyses and the description of an advanced measurement concept using fibre optical sensors for full‐scale beam tests.