The real time adaptive control algorithm of power spectral density (PSD) replication is presented based on Kalman filters to improve the control precision of the vibration control system. The finite impulse response (FIR) filters are designed with the reference PSD. The time domain drive signal is generated by filtering a series of independent white noise with the designed FIR filters. The Kalman filters are developed to obtain the inverse model of the vibration control system. The input signal of the vibration control system is updated based on adaptive inverse control method. The reference PSD is replicated in high precision by the reproduction of the time domain drive signal in the output of the system. The test results of PSD replication show the effectiveness of the proposed algorithm.
Wind tunnel tests were employed to study wind-induced interference effects on two adjacent cooling towers. The technique of adding roughness on model surface was applied to compensate for the Reynolds number effect due to model tests. Then the POD method was used to interpolate the wind pressures on the towers. After that, drag coefficients, lift coefficients and base shear coefficients on the isolated tower and two adjacent towers were calculated. Based on these coefficients, interference factors with respect to distances between two towers and wind azimuths were analyzed. Results show that, for the isolated tower, the mean drag coefficients are quite large whereas the mean lift coefficients are nearly zero. However, the mean-root-squares of drag coefficients and lift coefficients on the isolated tower are comparative in the magnitude. For two adjacent towers, the interference factors of mean and dynamic drag coefficients are almost the same. Most of the interference factors of dynamic lift coefficients are bigger than 1, while the biggest value reaches 1.75.
Unloading supporting system is important for semirigid structure, such as suspen-dome, during construction. Thus a failure criterion is presented for standard suspen-domes under unloading impact load. Using the criterion, analysis on the effect of unloading rate on the structure dynamic stability is developed adopting the Ansys software. The results that using direct unloading will be unsafe at some extent, improper unloading can cause structure failure are drawn. And further the structure failure mode and corresponding early warning system are obtained for unloading impact. Research for unloading failure mode and failure mechanism of a project case is presented, which verified the method obtained in the paper advisable and effective.
The underground tunnel and cable in the city is complex, mass transit or inter-city high-speed railway would be built above the underground tunnel and cable. Beijing-Tianjin High-speed Railway was regarded as an example to research the dynamic influence which was applied by the vibratory load of high-speed train on the underground tunnel and cable. Using coupling dynamics, the vibration analysis model of vehicle-track coupling system was built, and the dynamic response of vehicle-track coupling system caused by the high-speed train was calculated. On the basis of finite element theory, the pile-slab-soil-tunnel longitudinal-transverse-vertical spatial coupled dynamic simulation model was built. The load spectrum, which was obtained by using the vibration analysis model of vehicle-track coupling system, was used as external motivation and acted on the dynamic simulation model, and the dynamic response of cable tunnel was researched. The results show that cable tunnel under pile-slab structure would not be influenced unfavorably by dynamic action of high-speed train vibratory load after the operation of Beijing-Tianjin High-speed Railway.