Parametric tools could significantly increase efficiency in the design process within the construction industry, especially with prefabricated elements. Efficiency is also searched for in material use. An element that uses its material very effectively is a structural insulated panel (SIP). However, the synthetic polymers used in already existing panels are not very sustainable. The new climate agreements push producers into making more sustainable choices. Due to this, Kingspan Unidek is experimenting with a bio-based insulation material integration into the SIP. A new structural insulated panel with OSB/3 faces and a Steico wood fibre polyurethane resin insulation core is being developed. In this thesis, the panel’s behaviour is analysed for construction purposes under axial and transverse loading experimentally, analytically and through modelling. The behaviour of the panel is analysed for residential building applications, and the possibility of using parametric modelling tools in the design process for SIPs is assessed.
The analysis is performed by using four main methods – full-scale experiments under eccentric axial loading by Kingspan, models on Karamba3D and RFEM, and analytical calculations with Timoshenko beam theory, shear beam equations and rod in compression equations. The failure methods are analysed with hand calculations from sandwich panel theory. The Karamba3D model is developed by using shell and beam elements since it is not yet possible to model layered materials. The material is defined by the user and the core is modelled as beams which are scaled to match the Timoshenko beam equation results.
The faces exhibited a separate behaviour during the experiments under low eccentric axial loads suggesting a delamination failure or a core failure. The failure occurred during an eccentric 18 kN/m axial loading which caused the faces to behave separately. The core has very low strength properties compared to other conventionally used SIP insulation materials which are at least twice as strong as the Steico insulation board. Additionally, the analytical calculations showed that the panel has very low transverse loading capacity as a result of core shear failure – a maximum distributed load between 0.1 kN/m to 2.5 kN/m can be applied depending on the analysis method. These findings confirm that the panel could only be used with the application of through-thickness stiffeners. The developed Karamba3D model successfully reproduced the experimental results, but the model should not be used for failure analysis since local failures or interface failure is not described. Timoshenko beam theory and the RFEM model showed a good correspondence for transverse loading, but a bending test should be performed to confirm the results. The RFEM model could not show the SIP behaviour under axial loading but did exhibit a trend in deflection results towards where a local failure could occur. The conventional sandwich panel theory overestimated the panel resistance based on the experimental results and the modelling results.
The panel in this form could only be applied if through-thickness stiffeners are used to strengthen the panel or if the core material is significantly improved. However, there is a possibility that the separate behaviour by the faces could be avoided by avoiding eccentric loading and only applying centric loading. It would be necessary to test the panel for failure to get a better understanding of the failure modes and to further validate the model values. Additional testing to confirm the failure method would be testing the material properties of the Steico material, and the bond strength of the interface between the faces and the core. The model has the potential to be used for analysing all different sandwich structures, but would need to be further verified with different materials.