Rod-shaped connecting devices made from glass fibre reinforced plastic (GFP) represent an innovative solution for joining the precast shells of sandwich elements together. During the element’s construction phase, they assume the function of a formwork anchor and, in the panel’s final state, they act as load-bearing anchors for the facing shell. The prerequisite for realistically dimensioning the connecting device and its anchoring in the concrete shells is precise knowledge about the forces acting upon it. The decisive factor in dimensioning the pattern of these connecting devices is, as a general rule, the evidence gained under fresh concrete pressure loading conditions during the element’s construction phase. The following report will present research findings in respect of steel reinforced concrete sandwich wall panels with the subsequent addition of in-situ concrete. It will be demonstrated that fresh concrete pressure remains proportionally as a tensile force in the connecting devices. Allowance must thus be made for it as a loading condition in the documentary proof of the panel’s final state. A suggestion for computing the tensile force of the connecting device will also be made.