1. EN 14399 is a set of European standards that governs the preloading and torque tightening of high-strength bolted connections in steel structures. These standards are crucial in ensuring the safety and reliability of such connections, as they provide guidelines for proper installation techniques and procedures. EN 14399 covers a wide range of topics, including bolt dimensions, material properties, and testing methods, all of which are necessary for achieving the desired level of performance in structural connections. By adhering to the requirements set forth in EN 14399, manufacturers and engineers can be confident that their bolted connections will meet the necessary strength and durability criteria for their intended applications.