Connection techniques of reinforced precast concrete elements

The development of new materials and, in particular, new construction principles is opening up new avenues, especially in the field of precast construction, which is also becoming increasingly important in Germany. Whereas in classic modular construction, entire room modules are prefabricated based on steel or wooden frames. In solid construction, this represents a specialization that quickly reaches its limits due to the permissible transport weight. As an alternative, system components can be connected and provide a high degree of flexibility. Decisive for the design of such prefabricated structures is, in addition to the structural design of the components, is the structural design of the nodal points, and the consideration of construction conditions (e.g., transport anchors or assembly aids). On the one hand, it must be possible to design nodal points to suit the construction site. On the other hand, they must meet the requirements in the ultimate limit states and serviceability limit states so that all forces and moments that occur can be safely transmitted.

There are already a large number of tried-and-tested systems for connecting precast reinforced concrete elements. Precast elements are often connected utilizing a wet grouting process. This method has certain disadvantages, such as longer construction times due to the mortar/concrete setting times and the lack of deconstructability of the elements. Another possibility for connecting reinforced precast concrete elements are bolted connections. Against the sustainability and a possible reuse of the precast concrete elements, these are particularly suitable. They also have the advantage of faster assembly and the immediate load-bearing capacity of the connection, and the associated elimination of assembly aids. However, new challenges also arise from the fact that no subsequent grouting of the joint is required. On the one hand, corrosion-resistant materials’ durability must be guaranteed (e.g., stainless steel) for bolted connections. Likewise, mechanical connections must meet all thermal, sound, and fire protection requirements.

Due to the increasing importance of technical building equipment, reliable components are increasingly being planned and designed with integrated cable openings. This is particularly interesting for industrial prefabrication and can impact connection techniques if, in addition to the structural connection of precast elements, lines and pipes are also to be connected.

Using slender precast elements made of textile concrete, buildings can be erected in a more space-saving manner and saving material, thus increasing the usable area while maintaining the same floor space. Due to the lack of a normative basis, there are only a few connection systems for textile-reinforced concrete precast elements with a corresponding building authority approval. Although their weight reduces the connections’ load, the external loads must be safely transferred utilizing fasteners in very slender cross-sections with a minimum embedment depth of only a few centimeters. For this reason, connection systems for conventional reinforced concrete components with a generally considerable embedment depth cannot be readily applied to textile-reinforced concrete components. The same applies to load transfer components, connecting parts, and, in particular, transport anchors.

Within this consortium project’s scope, the advantages and disadvantages of different connection techniques for precast elements will be worked out and compared. Based on this, nodal points of precast concrete construction are to be optimized by the new or further development of connection techniques.

This project was successfully completed.