Slip strength of COR-TEN and Zn-coated steel preloaded bolted joints

Knowledge of the effective slip strength is a crucial safety issue when a bolted connection is designed to work by friction. Even if technical standards indicate the necessary tightening torque to obtain the desired preload, experimental relationship between bolt torque and preload is required in many cases where surface and bolt conditions are uncertain. In this work, the torque-preload relationship and the effective slip factors of bolted joints operating under non-standard surface conditions, namely COR-TEN and Zn-coated plates, are determined experimentally, and compared with standard as-rolled data. Results indicate that the requirements of design standards are not always conservative, making experimental characterization of the joint necessary.