EN 14399 is a European standard that specifies the requirements for high-strength structural bolting assemblies for preloading. These assemblies are commonly used in the construction industry for steel structures and connections.

The standard was first published in 2005 and has since been revised several times, with the most recent version being published in 2018. EN 14399 covers a wide range of bolt sizes, from M12 to M36, and includes various types of bolts such as hexagon head bolts, torsion bolts, and anchor bolts.

The standard specifies the material requirements, mechanical properties, and testing methods for these high-strength bolts. It also includes requirements for the design and dimensions of the bolt and the corresponding washer and nut.

EN 14399 is an essential standard for ensuring the safety and reliability of structural connections in buildings and other steel structures. It is used by engineers, architects, and construction companies to ensure that the bolts used in their projects meet the necessary strength and quality standards.

In addition to the requirements for the bolts themselves, EN 14399 also includes guidelines for the installation, tightening, and inspection of the bolt assemblies. This ensures that the bolts are installed correctly and maintain their preloading force, which is crucial for the stability and integrity of the structure.