ResearchResearch projects
Streckgrenzgesteuertes Anziehen von geschraubten Verbindungen M12 bis M72 im Stahlbau

Yield-controlled tightening of bolted connections M12 to M72 for steel construction

Led by:  Elyas Ghafoori
Team:  Christopher Schierl
Year:  2020
Funding:  AiF - Project sponsored by BMWi
Duration:  01.01.2020 - 30.06.2022

The fields of application for pre-stressed HV-assemblies with the corresponding bolts in steel construction are cases of bolted connections subjected to fatigue loads, e.g. expansion joints of bridges as well as onshore and offshore wind turbines. The level of the pretensioning force is of decisive importance for the magnitude of fatigue loads which the bolts are subjected to during the structure’s service life time. Ensuring a sufficient level of preload force is therefore of great importance in order to guarantee a permanently safe and low-maintenance bolted connection. By using the yield controlled tightening method, the bolt is tightened up to its yield point and thus high preload force, favourable for the fatigue life, is achieved.

In the steel construction practical framework the process safety of yield controlled tightening as well as the influence on structural integrity of HV-bolts is not yet investigated. Thus, the yield controlled tightening is not regulated by structural design standards.

The aim of this research project is to develop normative basis for process-safe yield-controlled tightening of HV-bolted connections as well as the validation of the structural integrity of HV-bolts with diameters M12 to M72 for steel construction.

Research institutions:

  •   Institute for metal and light weight construction, University Duisburg-Essen
  •   Institute for steel construction, Leibniz University Hannover