Frame with a reduced number of welds, bearer for such a chassis, and process for making such a bearer

Girder has central full height section, and two reduced height sections created by friction welding process. Chassis has 2 girders (1), each consisting of single profile initially of constant height. This has core extending vertically, and 2 wings (3,4). Core of each profile has first part (40) with full initial height, and part at each end (34,44) of reduced height. One wing and core are linked by weld (33,43) obtained by friction welding. Reduced height sections are linked to the main full height section by a curved section (32,42). An Independent claim is also included for the method for manufacturing a girder.