Optimisation of connections by increasing friction in the shear plane

As part of a research project, connections were optimised by increasing the friction in the shear plane through surface modification. Therefore, many different surface modification processes were initially analysed and tested for their applicability, especially on an industrial scale. The various surfaces were quantified by friction tests and both static and kinetic coefficients of friction were determined. It was found that surfaces with uniform, even structuring are preferable to surfaces with strong, punctual structuring. The first step was to identify suitable surface finishes by means of push-out tests. Further connection tests were then carried out with these surfaces to investigate the behaviour of inclined screws and increased friction in the shear plane. This enabled group effects such as block shear failure to be investigated and ruled out and new types of failure, such as transverse compression failure under the connector plates, to be identified. Increases in load-carrying capacity of up to 43 % and increases in stiffness of up to 29 % were determined due to increased friction in the shear plane. Using an analytical calculation model, the load-carrying capacity of the connection could be determined well and the evaluation of the results showed that the static coefficient of friction determines both the average load-carrying capacity and the characteristic load-carrying capacity well. Fatigue tests to determine the long-term behaviour of connections with inclined screws and increased friction in the shear plane showed that the friction is still activated even after a longer period of time and participates in the load transfer.