Development of an Easy-to-Use Design Tool

Analysis of Load-Bearing and Deformation Behavior of Sandwich Elements

Fig. 1 Composition of a cavity wall element with GRP anchors [7].Abb. 1 Aufbau eines Hohlwandlementes mit GFK-Ankern [7].

Fig. 2 Overview of possible
deformation figures of a
sandwich element [9].
Abb. 2 Übersicht über die möglichen Verformungs-
figuren eines Sandwichbauteils [9].

Fig. 3 Modified stress-strain curve of reinforcing steel to consider the tension-stiffening effect.
Abb. 3 Modifizierte Arbeitslinie des Betonstahls zur Berücksichtigung des Tension-stiffening-Effektes.

Fig. 4 Specimen for testing the shear strength of insulating materials in accordance with DIN EN 12090.Abb. 4 Versuchskörper zur Prüfung der Scherfestigkeit von Dämmmaterialien nach DIN EN 12090.

Fig. 5 Approximate load-deformation curves for polystyrene used as an insulating material (cf. [6]).
Abb. 5 Approximierte Kraft-Verformungs-Beziehungen für den Dämmstoff Polystyrol (vgl. [6]).

Fig. 6 Load-deformation curves for one GRP anchor in shear.Abb. 6 Kraft-Verformungs-Beziehungen für schubbeanspruchten GFK-Anker (1 Anker).

Fig. 7 Comparison of calculated deflection curves.
Abb. 7 Vergleich der berechneten Durchbiegungsverläufe.

Fig. 8 Calculated variables of state of the structural component (standardized).Abb. 8 Berechnete Zustandsgrößen des Tragelementes (normiert).

Fig. 9 Set-up of the component test [7].Abb. 9 Versuchsaufbau des Bauteilversuches [7].

Fig. 10 Comparison of load-deformation curves
determined in the test and
recalculation.
Abb. 10 Vergleich der Kraft-Verformungslinien in Versuch und Nachrechnung.

 Sandwich elements can be produced quickly and cost-efficiently under the favorable conditions provided at the precast plant, and they conform to highest concrete quality standards. These are compelling arguments in favor of this method compared to cast-in-situ construction. However, a realistic representation of the load-bearing behavior of sandwich elements is complex, which is why it is not usually carried out in the practical design of elements. This article presents a computation model for sandwich elements and derived findings that were included in a thesis submitted to the Institute of Concrete Structures and Structural Engineering (Prof. Dr.-Ing. J. Schnell) at Kaiserslautern University of Technology.

Load-bearing behavior of sandwich elements

The load-bearing behavior of random, layered structural components is determined by the stiffness of the individual layers and by the type and extent of joint actions of these layers.

Compared to the relatively rigid covering layers of sandwich elements made of concrete, the contribution of the insulation layer to their overall load-bearing capacity can be largely neglected. However, the insulating layer creates a shear bond between the covering layers by means of interlocking and/or adhesion, which is why bending moments acting on the overall...