On the basis of experimental results in this thesis by Christian Keindorf come for the sandwich tower sections that are to be connected with steel tower sections, several material combinations considered. In the variant with an elastomer filling no shear ribs and adhesion promoters are required because the tested composite material has an extremely high tensile bond strength on grit blasted steel surfaces.
Alternatively, a grout with adhesion-promoting additives in the connection area are used, which also should have a good pump and fluidity and high compressive strength. For this variant, shear web, recommended as the Grouted Joints to the strut bearing capacity to significantly increase both in the ultimate limit state and serviceability limit state of fatigue. This effect was demonstrated by measurement / 2009 explained in detail in Bautechnik Heft 11/2009 , with reference to the experimental results, a design proposal was derived.
In an onshore location, for example, can a foundation section a frictional transmission between sandwich tube and foundation are obtained. In this case ("reverse power flow") the forces and moments are analogous to the connection to the top steel tower section is initiated.
The use of a sandwich tower section is basically also possible offshore, whereby the sandwich joint can be used as a connection to the Monopile or central pipe of a Tripods. However, for this, the sandwich joint must meet the special design requirements of offshore towers. However, this new joint variant could save additional ring flanges and bolts. Many years of transferable experience with the required assembly technology already exist in the case of realized grouted joints for WTGs.