BT-Spannschloss® system – project with timber hybrid construction method

Technologien und Beratung für den Betonbau - B.T. innovation

BT-Spannschloss® system in use in Germany's largest project with advanced timber hybrid construction method

In a current project, the Siemens Campus II in Erlangen, the ring beams are produced using the BT turnbuckle. Siemens Campus II comprises five buildings with around 70,000 sqm of gross floor space. The buildings have five to seven storeys. There, groups of five BT turnbuckles M12 are used throughout to form the ring beam.

When installing ceiling elements, whether weight-reduced hollow core slabs or solid concrete slabs, a ring anchor is usually required. It is common to form the ring anchor in the joints between the ceiling element and the wall or edge formwork. For this purpose, reinforcement bars are inserted in the required number and diameter with corresponding cover lengths and cast with concrete. For larger tensile loads, welded connections of the ring beam are carried out.

However, the subsequent installation of reinforcement and grouting slows down the construction progress and can even lead to downtimes, due to the curing times to ensure the required concrete strength. By using the BT-Spannschloss® system, this delay can be completely prevented. The ring anchor is already integrated into the floor elements during prefabrication.

CREE Deutschland GmbH, a subsidiary of the Zech Group, constructs buildings using innovative wood hybrid construction methods. The first buildings erected still had a ring beam design by means of large grouting zones in which the reinforcement was connected with the usual lap joints.

In a current project, the Siemens Campus II in Erlangen, the ring beams are therefore produced using the BT turnbuckle. The chosen arrangement of five BT turnbuckles has procedural, design and structural advantages that convinced CREE:

Process engineering:

The production of the prefabricated floor elements is simplified and thus labour costs are saved: the recess body is fixed to the formwork and during concreting no additional expenditure is required for shuttering the grouting zone and removing concrete.


The dimensions of the BT turnbuckle allow it to be installed in the 10 cm thick concrete transom while maintaining the required concrete covers for the verification of the 90-minute fire protection without any further measures.

Construction technology:

The BT-Spannschloss® is connected by means of standard metric screws and is immediately load-bearing. In addition, it is possible to accommodate production and installation tolerances between the prefabricated elements.

Learn more about this project here.

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