The Bolt Pretension study step is a special case of a Stationary study step, where the special degrees of freedoms used for modeling prestressed bolts are solved for. In all other study types, these degrees of freedom are inactive. Typically, you include a Bolt Pretension study step as the first step in a study in order to simulate the state after the assembly of a bolted joint. You can then add any other types of study steps for computing the effects of the service loads.