The formulation of a beam on which a pair of piezoelectric segments bonded is presented. The method of transfer matrix is adopted to study the structural responses of the surface-mounted actuation beam induced by an external force on the beam and by a voltage on the actuator. Furthermore, the modal frequencies and the corresponding mode shape functions of the beam also are obtained by the method. The orthogonality of any two distinct sets of mode shape functions of the beam is shown. The method of modal analysis is presented to study the forced vibration of the beam due to a concentrated transient force. The effects of length, location and thickness of the piezoelectric pairs on the structural responses and the modal frequencies of the beam are investigated.