Tension in screw because of moment in section

Hi,

In a section of a beam with a rectangular hole which has got crack (see attached picture); Moment and shear are specefied. I can undrestand why we have tension in the screw because of the shear but why do we have tension because of moment in the screw? Can anybody explanin me why moment in the section can cause tension in the screw which should be accounted for in the screw design.

Thank you,

Parisa