Figure 12. Frequency responses and RMS voltage outputs of Branch F (Table 2) in Case D (Table 1) when the base acceleration is 10 m/s 2 . (a,b) Show sweep responses, stroboscopic points, and HBA solutions of Beam 1 and Beam 2, respectively. (c,d) Depict RMS voltage outputs of Beam 1 and Beam 2, respectively. Stable and unstable HBA solutions are plotted by the solid line and dot-dashed line, respectively. In (a,b) , Zone B means that the branch belongs to Zone B in Fig. 11, and the triangle markers indicate the bifurcation points as follows: sn saddle-node bifurcation, ns Neimark–Sacker bifurcation.