This paper presents an improved model for the one-dimensional behavior of a membrane mirror strip actuated using a piezoelectric bimorph. This model specifically accounts for the changes in physical properties of the membrane strip at the location of the piezoelectric bimorph. The membrane strip is modeled as a pinned-pinned beam under tension and the finite element method (FEM) is used to represent the system mathematically. The frequency response obtained from the proposed model is shown to be in agreement with experiments. Furthermore, the importance of including local mass and stiffness effects is demonstrated.