This is the setup used to test all bolts in tension. The wedge washer is restrained by multi-point constraints to an unseen point above. This allows the washer to rotate in a circular motion around the above point but nothing else. A similar constraint is placed on a section of the bolts threaded region. This allows the bolt to move in a circular motion about a lower unseen point as displacement controlled tension is applied.
The dampers shown at the right represent the friction in the pinned joints (where the multi-point constraint connect above and below).