Experimental and analytical analysis of layered concrete beams with partially stiff interfaces

The behaviour of layered flexural concrete elements is significantly influenced by the characteristics of the interface between layers. The impact of the interface must be considered during the analysis of such structural elements. This study presents an analysis of layered flexural element interface characteristics, flexural layered element behaviour and a novel analytical approach to predicting the deflection of layered concrete elements. The proposed method includes (1) a model describing the interface behaviour and (2) a deflection model for layered flexural elements. To validate the analytical models and examine the structural performance of layered concrete elements, six layered concrete beams were constructed and tested. The beams were categorized based on their interface connectors: type P beams with connectors perpendicular to the interface, and L1 and L2 beams with connectors resembling lattice girder. Additionally, each beam type was constructed with two cross-sections configurations: one with 50 mm and 200 mm layers, and another with 80 mm and 170 mm layers. Experimental results indicated that L2 beams exhibited the highest capacity before adhesive interface failure (reaching 44.3 kN and 36.2 kN load) and performed well when friction and dowel action governed the interface behaviour. Conversely, L1 beams showed the lowest adhesive resistance (reaching 25.6 kN and 25.1 kN load), while P beams demonstrated moderate performance (experiencing adhesive failure at 31.7 kN and 29.4 kN). Additionally, beams with thicker bottom layers exhibited higher flexural capacity across all behavioural stages. Moreover, different connector arrangements were the cause of different beam cracking patterns. Analytical models were used to predict the behaviour of layered beams. The analytical results were similar to the experimental results. Furthermore, differential concrete layer shrinkage was considered in the analytical calculations. The reduction in interface adhesive resistance due to differential shrinkage was found to be in the range of 0.56–0.62 MPa. • Layered concrete beams with varying connector setups and layer thicknesses tested. • Connector setups and layer thicknesses affected beam capacity and cracking. • Novel model proposed for predicting interface behaviour. • Novel deflection model proposed for flexural layered concrete elements.