This paper presents the design, characterization, and application of periodic piezoelectric actuator arrays for structural health monitoring. In the proposed array configuration, all elements are activated simultaneously to achieve strong frequency-dependent directional actuation, which allows beam steering through a sweep of the excitation frequency and limited hardware requirements. The array enables in situ monitoring of critical components through strongly focused actuation and directional scanning capabilities. The concept is illustrated for a selected design with quadrilateral topology on an isotropic plate. The application to composite panels is also specifically discussed by illustrating the complexity of the corresponding dispersion properties, which suggest design challenges for mode tuning. A quadrilateral design is tested for excitation of the mode on a selected lay-up sequence to illustrate the generality of the proposed concept and its applicability to composites.