This document specifies, together with EN 14399-1, the requirements for assemblies of high-strength structural bolts and nuts, with large width across flats, of system HR or HV, including the requirements for the general dimensions, tolerances, materials and performance for two grades, H8 and H10, of compressible washer-type direct tension indicators, nut face washers and bolt face washers suitable for preloaded joints. The assemblies include the nominal thread sizes M12 up to and including M36 and property classes 8.8/8, 8.8/10 and 10.9/10.
Bolt and nut assemblies to this document have been designed to allow preloading of at least 0,7 fub × As according to EN 1993-1-8:2005 (Eurocode 3) and to obtain ductility predominantly by plastic elongation of the bolt for system HR according to EN 14399-3 or by plastic deformation of the engaged threads for system HV according to EN 14399-4; also countersunk and fit bolts according to EN 14399-7 and -8 respectively.
Bolt and nut assemblies conforming to this document may include washer(s) according to EN 14399-6 or to EN 14399-5 (under the nut only).
The purpose of the direct tension indicators is to show that a defined preload is achieved in the bolt. The direct tension indicator can be used alone or with bolt face washers or nut face washers conforming to this standard. In either case it is essential that the direct tension indicators are used as part of an assembly in accordance with EN 14399-1.
To comply with EN 14399-1, it is essential that the assemblies are supplied by one manufacturer and include bolts, nuts, washers and direct tension indicators.