UNIVERSAL CONNECTION ON GLUED-IN STEEL RODS FOR TIMBER STRUCTURES WITH CROSS LAMINATED TIMBER PANELS

The connection decision presented in the paper aims at the development of a new solution for anuniversal connectorinCLT timber structures, which offers the possibility of quick and easy installation and assembly, as well as easy disassembly and reuse. This solution shall contribute to the necessary reconstruction of the damages in Ukraine and facilitate the quick restoration of housing as well as providing a long-lasting sustainable and circular connection solutions. The developed connector is a unit in the form of a steel plate on glued-in rods, that are embedded in the CLT panels. This allows to connect CLT panels in various arrangements together or to other building parts such as foundations or concrete cores. Connections with glued-in rods are widely used in Eastern European countries, especially in long-span timber structures for buildings of various types. One of the barriers for the greater utilisation of timber in construction is that engineers, architects, contractors, and authorities have little experience with the construction material timber and its utilisation in high-performance structures compared to other conventional building materials such as concrete and steel. Often the experience, skills, and workmanship regarding timber on the construction site are limited. Besides training also the development of simple connection and detailing solutions need to be developed, that can be easily and safely applied by unskilled personnel. Prefabricated connections with bonded-in rods or bolted connections are examples of such solutions. The project ReConnect - Efficient connections for modular prefabricated timber buildings to help reconstruction in Ukraine, has the objective to develop a novel connection system for timber members that makes it possible to adopt the concepts of reusability, adaptability and circularity of members in timber structures. By optimizing the connection layout, we intend to enhance the performance towards low damage and to avoid brittle failure modes in the timber. The prefabrication of the proposed connection in the factory and its uniform spacing along the edges of CLT panels makes it possible to produce entire series of unified building components of different sizes and layout solutions. To consider the variety of loading states acting on the connector, different tests are performed at Tallinn University of Technology and at O.M. Beketov National University of Urban Economy in Kharkiv. The preliminary calculations of the FE-model of the 3-storey case-study building with the proposed connector with glued-in rods show that the resulting forces in the connections do not exceed the estimated theoretical values of load-carrying capacity derived from the standards in pull-out and shear loading. The proposed geometry is suitable without modification for the case-study building with 3-5 floors, where the forces do not exceed the analytical and experimental resistances. For tall buildings in platform construction, when the load between the walls exceeds the crushing strength of the timber perpendicular to the grain of the floor panels, it is necessary to insert steel tubes between the connector plates that transfer the loads through the floor panel. This solution has been used already in many cases for the transfer of loads through floors between columns. The proposed new type of connection system is universal, easy to implement in production and can be used (with minor modifications) in buildings of 5 floors and above. The glued-in rods can be replaced with screws if necessary. However, it should be considered that the costs of connections with glued-in rods is much cheaper in Ukraine than connections using fully threaded self-tapping screws.