<p>The bolt has a round-shaped bearing portion (2) comprising three rounded-off projections (3) that are tangentially displaced around 120 degree. Three pockets (4) are provided in an inner side of the bearing portion and tangentially displaced around 120 degree. The pockets symmetrically run in a longitudinal direction and parallel to the projections, where radial connection regions of the pockets form a deformation body (17). Strain gauges (5) are designed as bending stress measuring elements and formed at inner outer surfaces of the radial connection regions.</p>