The effect of entrained air in the hydraulic brake system of a platoon vehicle in a controlled braking manoeuvre was theoretically investigated. The actuator dynamics with the load inertia was considered, and non-linear and linearized system equations were derived in dimensionless form. It was found that the principal resonant critical frequency decreases as a result of the entrained air, and that the resonant peak amplitude increases as the air content increases. The decreased resonant frequency leads to a reduction in the bandwidth of the brake actuator. A stability criterion for the system reveals that the entrained air reduces the allowable open-loop gain, diminishing the stability in a closed-loop system. Numerical simulations for frequency response show that even small amounts of entrained air could drastically affect the braking performance.

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The responses of a cabinet for a reactor protection system under seismic loadings are analysed by using the finite-element method, and its dynamic characteristics are evaluated. Analysed modes are compared with the measured data from a resonance search test. The structural safety of the cabinet is evaluated considering the required response spectrums of the operation-base and safe-shutdown earthquakes. The transient response of the cabinet is analysed by utilizing the measured acceleration of the vibration table representing the seismic motion of the ground. Time histories of accelerations at the locations of major internal parts are extracted. The transient responses are compared with those from the seismic test and the results were found to closely represent the system.