Figure 4. Frequency response and HBA results of the conventional BEH when the base acceleration is 4 m/ s 2 . The values of Case A (Table 1) are used. (a) Shows sweep responses, stroboscopic points, and HBA solutions of Branch A, C, and D (Table 2). (b) Depicts the HBA results of Branch D when the solution truncation order, H , is set to be 1, 3, and 5 (Eqs. (6), (7)). Stable and unstable HBA solutions are plotted by the solid line and dot- dashed line, respectively. In (a) , the triangle markers indicate the bifurcation points as follows: sn saddle-node bifurcation, pd period-doubling