Figure 16. Frequency responses of Branch C, E, F, and I (Table 2) in Case E (Table 1) when the base acceleration is 9 m/s 2 . (a,b) Show sweep responses, stroboscopic points, and HBA solutions of Beam 1 and Beam 2, respectively. Because Branch E is unstable in Case E, only HBA results are plotted. The solid line represents stable HBA solutions, and other lines indicate unstable HBA solutions of each branch as follows: dot-dashed line—Branch C, bold dot-dashed line—Branch E, double-dotted line—Branch F, dotted line—Branch I. The triangle markers indicate the bifurcation points as follows: sn saddle-node bifurcation, pd period-doubling