<p>The rotational ductility of Ultra-High Performance Concrete-Normal Concrete (UHPC-NC) composite structures in the negative moment zones of prestressed concrete (PC) girder bridges is critically investigated in this study. Conventional elastic analysis methods often fall short of fully exploiting material potential, as they primarily focus on the ultimate bearing capacity of critical sections while neglecting the development of plastic hinges and the associated redistribution of internal forces. To address this limitation, an analytical model based on the Strip Method is developed. This model discretizes the cross-section into multiple strips, enabling accurate simulation of key mechanical behaviors, including the tensile hardening of UHPC, bond-slip between reinforcement and concrete, and shear transfer at the UHPC-NC interface. This approach establishes a robust mechanical basis for quantifying rotational capacity. A systematic parametric study is conducted to evaluate the effects of reinforcement ratio, material strength, and interfacial detailing on rotational ductility. The results show that the tensile reinforcement ratio is the primary control factor for rotational ductility. In contrast, its effects on initial stiffness and ultimate rotation angle are secondary. In contrast, the thickness of the cast-in-place UHPC layer exhibits a relatively minor impact on ductility. Furthermore, it is demonstrated that structural rotational ductility and energy dissipation capacity can be substaantially improved by optimizing parameters such as UHPC layer thickness, tensile reinforcement ratio, rebar diameter, and stirrup reinforcement ratio. This delineation provides clear guidance for the performance-based design of UHPC-NC connections.</p>