Figure 6. Harmonic distortions and their effects on simulations for root-mean-square (RMS) voltage calculations of Branch D (Table 2) of Beam 2 in Case B (Table 1). The k -th harmonic distortion means relative deflection amplitude of the k -th order harmonic with respect to the amplitude of the fundamental harmonic. (a,b) Show the third- and fifth-harmonic distortions of Branch D in Fig. 5, respectively. In (a,b), the dot- dashed line represents unstable solutions. In (b) , the asterisk denotes the maximum point of the fifth-harmonic distortion of Beam 2, and the frequency corresponding to the asterisk is used in (c–e) . For the simulations of the RMS voltage outputs, the base acceleration is increased from 4.4 m/s 2 , used in Fig. 5, to 11 m/s 2 . (c–e) Show the RMS voltage outputs of Beam 2 when the solution truncation order, H , is set to be 1, 3, and 5 (Eqs. (6), (7)), respectively. The red arrows indicate whether the RMS voltage output increases or decreases as the base excitation becomes