A rotor blade assembly for a wind turbine may include a first blade segment having a first joint end and a second blade segment having a second joint end, with the blade segments being coupled together such that the first and second joint ends are located at or adjacent to a joint interface between the blade segments. The blade assembly may also include a pre-loaded beam extending outwardly from the second blade segment across the joint interface such that the pre-loaded beam is received within the first blade segment. The pre-loaded beam may be compressed between the opposed internal structural components of the first blade segment such that a first engagement interface is defined between a first side of the pre-loaded beam and the first internal structural component and a second engagement interface is defined between an opposed second side of the pre-loaded beam and the second internal structural component.