Insulated concrete sandwich panels with gradient-distributed connectors: Analytical model

Insulated Concrete Sandwich Panels (ICSPs) have been widely applied in engineering due to their excellent thermal insulation, vibration isolation, and mechanical properties, where the upper and lower concrete wythes are connected by shear connectors to achieve composite action. The degree of composite action (DCA) of ICSPs is primarily governed by the shear stiffness of the connectors. Most existing studies enhance the composite action of ICSPs by increasing the usage of connectors, which in turn degrades the panels’ thermal insulation and vibration isolation performance due to the bridging effects. To address this issue, this study investigates the effectiveness of gradient-distributed connectors along the span direction to enhance composite action without increasing connector usage. An analytical model capable of considering non-uniformly distributed connector stiffness is developed to predict interlayer slip and structural deflection under bending conditions. The model is validated through both finite element (FE) simulations and comparison with existing experimental results. The FE and analytical results demonstrate excellent agreement and confirm that a gradient distributed stiffness, where stiffness increases from midspan toward the ends, significantly improves DCA. Under the test conditions, a linear gradient in connector stiffness increases the DCA by 22.35% compared to a uniform connector distribution. Parametric studies based on the analytical model further examines the effect of different parameters, including average stiffness of connectors K ave , concrete strength, the ratio of the interlayer spacing to the thickness of a single concrete wythe C ′ / t , and the length-to-width aspect ratio of the ICSPs L/b . Comparisons among linear, quadratic, and constant stiffness indicate that gradient distributions of connector stiffness consistently increases the DCA of the ICSPs. The most significant improvements are observed with low K ave , C ′ / t , and L/b , while quadratic distribution in connector stiffness gives higher DCA than linear ones. The enhancement effect diminishes as the structure approaches full composite action. The proposed analytical model offers a practical tool for optimizing connector layouts in ICSP design, enabling mechanical efficiency while maintaining insulation performance. • An analytical model for gradient-distributed connectors in ICSPs is developed to predict slip and deflection. • Replacing uniformly distributed connectors with a gradient layout increases the overall DCA by up to 22.35%. • Quadratic stiffness gradients outperform linear layouts, particularly in panels with low initial composite action.