In piezotronics, PN junctions usually possess both piezoelectricity and semiconductor properties. This allows them to be manipulated mechanically by external forces through the coupling between deformation and free carriers. For a conventional non-piezoelectric PN junction, however, the mechanical manipulation seems difficult to achieve. In this paper, we theoretically demonstrate that this problem may be addressed via structural design. A composite beam model consisting of a piezoelectric dielectric layer and two non-piezoelectric PN junction layers is proposed. Then its electromechanical response under three different types of shear loads is examined based on a one-dimensional phenomenological theory. Results show as expected that the electrical behaviors of the junction can be tuned mechanically when the external force is applied on the interface, which provides a new idea for the design of piezotronic devices. Further, the effects of the doping level, thickness ratio, and material combination are also investigated, providing a comprehensive understanding of the proposed composite model.