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Lightweight steel constructions made of sandwich panels are an economical solution for wall and roof claddings, especially in industrial construction. The panels consist of two thin sheets of steel and a core with thermal insulating properties. In the mounted state and at high temperatures on the outer face of the panel, damage to the components may occur due to blister formation. In a current research project, the influence of defects in sandwich panels with a PIR‐foam core is examined. This article presents the results of experimental tests regarding the influence of various parameters, such as face temperature, production defects and design of the longitudinal joint on blistering in sandwich wall panels with a PIR‐core. The aim is to identify the necessary conditions for the occurrence of blisters. Using an optical strain measuring method (Digital Image Correlation), the temperature‐induced deformations and strains in the covering nose of sandwich wall panels with hidden fastening are measured and will be analyzed with regard to blistering. First results reveal a significant dependence on the geometry and design of the covering nose. [ABSTRACT FROM AUTHOR]

Sandwich panels in the construction industry are used as roof and facade elements and usually consist of two thin face layers of steel and a thicker core of polyurethane (PU) or mineral wool in between. The PU core material is constantly being further developed. In addition to improvements in the physical properties, this further development also leads to changes in the mechanical properties. As a result, the design rules that were established for older foam systems must be reviewed at regular intervals. There is a great need for research into the temperature‐dependent behavior of the foam system. As these elements are used as roof and facade elements, they are directly exposed to climatic conditions. High temperatures are generated on the cover sheets due to solar radiation. The PU rigid foam changes its mechanical properties in this temperature range. Tests on small parts and components show a change in the stiffnesses and strengths, as well as the load‐bearing behavior under elevated temperature. Consideration of the temperature in the design is therefore of great importance. In view of the continuous further development of the foam system, statements regarding the core material from older research must be reconsidered. [ABSTRACT FROM AUTHOR]

Determination of the shear properties of sandwich core materials A comparison of the core materials of sandwich panels has revealed inconsistent relationships between their stiffness moduli at different core thicknesses. Therefore, two test methods for determining the shear properties of the core material of sandwich panels were assessed theoretically and experimentally. The results show that for the shear beam test according to EN 14509 a more precise definition of the load distribution plates is necessary and that the usual neglect of the indentation at the support is only justified for thin and medium panel thicknesses. The investigations on the square shear test have shown the influence of the eccentricity between the joint plane and the top edge of the specimen and resulted in the development of a new test setup. The findings from the investigations provide the basis for more realistic modelling of the load‐bearing behavior of sandwich panels in the future. [ABSTRACT FROM AUTHOR]

Moment support interaction of multi‐span sandwich panels Self‐supporting double skin metal faced sandwich panels are usually designed and installed as multi‐span beams. In this case, there is always an interaction at the intermediate supports between the compressional normal force in the face sheet and the support reaction orthogonally to it, which can reduce the bending capacity. Many effects influencing the reduced load‐bearing capacity are not taken into account in current approval practice (and design). Within a research project funded by the DFG, experimental, numerical and analytical investigations were therefore carried out on sandwich panels. The main influences on the reduced wrinkling stress under an applied transverse compressive load were quantified and a possible solution was identified in order to take them into account in the future, e.g. within the scope of the approval tests. [ABSTRACT FROM AUTHOR]

Examination of the interaction of bending and compression at the support of sandwich panels The interaction of bending moment and the compression at the support of sandwich panels is assessed experimentally. DIN EN 14509 [1] gives a 3‐point‐bending‐test in which the span depends indirectly on the thickness of the panel. The span is the decisive factor since it gives the ratio of moment to compressive force. Therefore, it was analysed how long the span shall be to represent real systems well. The parameter‐study led to the conclusion that the span might be between 1 m and 12 m for realistic results. DIN EN 14509 [1] usually asks for 4 m to 6 m. Tests were performed to improve the understanding of the relevant mechanisms [2–5]. The over‐ resp. under‐estimation of the span leads to deviations in the serviceability criterion of up to ± 20 % (wall) and ± 30 % (roof). Finally, a recommendation is given to consider these deviations in practical design. [ABSTRACT FROM AUTHOR]

Lightweight constructions made of sandwich panels became well established for roof and wall claddings of industrial structures. Due to their good heat insulation, their excellent weight to load ratio and high load‐bearing capacity as well as the economical manufacturing and erection process, sandwich structures are build frequently. Besides the mentioned advantages the linear manufacturing process of sandwich panels usually limits the possible building cubature to rectangular shapes. In an interdisciplinary project, architectural, civil engineering and mechanical engineering institutes of Technische Universität Darmstadt are working on a design concept building shell structures with linear manufactured curved sandwich panels. A preliminary study indicates that arched sandwich beams have a high potential regarding the load‐bearing capacity. The comparison between arched and single span sandwich beams shows that, even for asymmetric loads, resulting stresses in the two‐hinged arches are significantly lower than in the related simply supported single span beams. To verify the results of the numeric study full‐scale tests on curved sandwich panels will be performed. Furthermore, an assessment of the load‐bearing behavior of the panels joints loaded with axial forces is planned. Based on the results further numeric studies will be conducted to investigate the behavior of whole shell structures following the developed design principle by taking into account realistic load cases for exemplary building applications, giving special attention to asymmetrical loads. Moreover, further research regarding the requirements for supporting structures as well as for the connection between the shell structure and the supporting structure is necessary to take into account the high axial forces, which are not common in sandwich structures. [ABSTRACT FROM AUTHOR]

Das Ziel der durchgeführten Optimierung liegt darin, die mechanischen und geometrischen Eigenschaften der Sandwichbauteile so auf einander anzupassen, dass sich eine möglichst hohe Tragfähigkeit der Elemente ergibt. Gleichzeitig werden die entstehenden Materialkosten berücksichtigt. Eine parallele Berücksichtigung der Tragfähigkeit und der Materialkosten führt zu einer Mehrzieloptimierung mit zwei konkurrierenden Zielen. Zusätzlich fließen die Gegebenheiten, die aus den Produktionsprozessen und der Anwendung der Paneele resultieren, in die Berechnungen als Randbedingungen ein. Der Aufsatz basiert auf [1], wobei es sich um eine Optimierung von Sandwichwandbauteilen mit einem PUR-Kern und Stahldeckschichten handelt. Optimization of wall sandwich panels. The aim of the conducted optimization is an adjustment of the mechanical und geometrical properties of sandwich panels in a way that a high load bearing capacity of the elements can be achieved. At the same time the emerging material costs shall be considered. A simultaneous consideration of load bearing capacity and material costs causes an optimization problem with two competitive objectives. Conditions coming from the production processes and the use of the panels are intergraded in the optimization calculations as constraints. This article is based on [1], where an optimization of wall sandwich panels with a PUR-core and steel cover sheets is done. [ABSTRACT FROM AUTHOR]