Investigations into the tightening behaviour of weathered HV and HR bolting assemblies

In Europe, preloaded bolting assemblies for steel structures have to be verified by suitability tests according to DIN EN 14399-2. These tests are carried out under controlled laboratory conditions with properly stored bolting assemblies from the factory. However, improper storage on construc- tion sites lead to possible variations of the tightening behaviour, which may influence the suitability for preloading. At least some standards and guidelines as well as the manufacturers of bolting as- semblies indicate that uncontrolled exposure conditions can affect the lubrication performance of bolting assemblies resulting in altered friction conditions. Beside other impacts, exposure of bolting assemblies to different weathering conditions might affect the tightening behaviour. This contribu- tion presents results of investigations into the tightening behaviour of bolting assemblies which were improperly stored under outdoor weather exposure.