Metallic constructions - mechanical assembly processes

This second article deals with mechanical assemblies. These are fasteners consisting of cylindrical metal parts placed in holes in the parts to be assembled. These include bolts, screws, rivets, nails, etc.

The Constructions Métalliques articles on assembly methods have been subdivided into 2 further parts:

• [C 2 520] "Means of assembly;

• [C 2 522] "Welded assemblies".

These connectors transmit forces either by :

• abutment and contact pressure between assembled parts ;

• mobilization of friction between assembled parts ;

• shearing of fasteners ;

• assembler traction ;

• combination of these stresses.

A new body of standards recently adopted at European level, EN 14399, now authorizes the use of new types of high-strength bolts suitable for prestressing. While it is of course still possible to use the traditional HR bolts and HV bolts already specified in EN 1993, it may be interesting to use :

• HRC, known as "high-strength bolts with calibrated prestressing";

• Adjusted HV ;

• with preload indicator washers.

This whole range, which offers a greater variety of choices to metal fabricators, is explained in detail here, their mechanical characteristics are compared and the criteria for choosing these different types of bolt are specified.

The article begins with a presentation of traditional ordinary and HR bolts, their mechanical behavior and the associated design rules as defined in Part 1-8 of Eurocode 3. Other high-strength bolts suitable for prestressing are then explained, along with all the mechanical connection methods currently referenced in EN standards. These include :

• HV bolts ;

• HRC bolts ;

• fitted bolts ;

• preload indicator...