Abstract: A boom (1) is used for receiving loads on the end thereof. The boom (1) has a metal boom hollow profile (2) extending along a boom longitudinal axis (3), and also a reinforcing layer (7) made of a fiber-plastic composite, connected to the boom hollow profile (2) at least in sections. At least one sensor element (12) is arranged in the region of the reinforcing layer (7). The sensor element (12) is used to detect strains in the boom (1).

Abstract: The invention relates to a method and to a device for attaching and removing an additional device comprising individual elements to and from the main jib of a mobile crane using no auxiliary crane. In the method according to the invention, a partial piece (2.1) of the additional device (2) composed of partial pieces is raised into an inclined position while being rotated about an upper pivot point (C), and the head (1.2) of the main jib (1.1) is bolted to the lower end of the inclined end of the partial piece (2.1) of the additional device (2) facing the mobile crane so as to be able to rotate. Using a hoist cable (7), all partial pieces (2.1 to 2.7) are raised in alignment with respect to each other and the main jib (1.1), and are bolted to each other in this position and to the main jib. The invention furthermore relates to a displacement device for carrying out the method according to the invention.