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Real-time hybrid simulation (RTHS) is recently applied to study the vibration of the vehicle–bridge coupling system, where bridges and the vehicle are the numerical and experimental substructures respectively. Inevitable time delay of the boundary loading imposed to the experimental substructure will greatly affect the accuracy and stability of RTHS. To minimize the time delay effects, this paper proposes a recursive prediction optimal (RPO) compensator based on optimal control and recursive least squares. The numerical simulation of the RTHS of the vehicle–bridge coupling system is conducted using MATLAB/Simulink. The performance of the RPO method is compared with three traditional time delay compensation methods (i.e. the polynomial extrapolation (NI), the inverse compensation (IC) and the derivative feedforward (DF)) through both open-loop and RTHS simulations. The RPO method shows the best compensation performance in the frequency range up to 20[Formula: see text]Hz.

Shaking table substructure testing takes the substructure with complex behavior physically tested, with the behavior of the rest structural system being numerically simulated. This substructure testing allows the payload of a shaking table being fully utilized in testing of the most concerned part, thus significantly increases its loading capacity. The key to achieve a successful shaking table substructure test is to coordinate among the substructures, specifically, to satisfy compatibility, equilibrium, and synchronization at the boundary between numerical and experimental substructures. A number of studies have focused on the essential techniques of shaking table substructure testing, and several applications have been carried out. Nonetheless, its progress is still in the preliminary stage, because of the limited applications using multi-directional shaking tables on large-scale specimens. This paper reviews a series of shaking table substructure tests and their associated implementation aspects including hybrid testing frameworks, time integration algorithms, delay compensation methods, shaking table and actuator control schemes and boundary force measurement methods. The key techniques required for a successful test are also stressed, such as the force control of actuators to coordination among the substructures. Finally, challenges for future studies and applications are identified and presented.

During a real-time hybrid simulation (RTHS), inevitable time delay of actuators when responding to a command will reduce the accuracy of test results and sometimes even cause unstable testing. The inner-loop controller of an actuator is generally capable of eliminating the effects due to small time-delays. However, if a test specimen behaves nonlinearly, accuracy of RTHS results will be impaired. In addition to the uncertainty of test specimens and transfer system, measurement noises of the displacement and force sensors also require a robust external controller for RTHS. In this paper, a robust linear-quadratic-gaussian (LQG) controller with a Loop Transfer Recovery (LTR) procedure and a polynomial-based feedforward prediction (FP) algorithm is proposed to compensate the adverse effects due to time delay and uncertainties within the RTHS testing system. The stability and robustness of the proposed controller are analysed in the frequency domain using the Nyquist curve and the Bode diagrams. Numerical simulations are then carried out on the benchmark problem using both the proposed robust and the conventional LQG controllers and their performance is compared using the nine evaluation criteria. It is demonstrated that the robust LQG (RLQG) controller outperforms the conventional LQG controller in terms of compensating the parameter uncertainties in the testing system and achieving accurate RTHS results.

Train-track-bridge interactions (TTBIs) in high-speed railways affect the response of the train on the bridge and involve complicated dynamics. This study introduced an improved real-time hybrid simulation (RTHS) method, wherein a physical train model was tested on a shake table, while the dynamics of the track-bridge structure were determined numerically. The moving load convolution integral method (MLCIM) was proposed for the real-time calculation of the track-bridge structure dynamics independent of the complexity of the numerical model. The results obtained using the MLCIM were compared to those obtained using the traditional finite element method to verify its accuracy and efficiency. Next, the TTBI characteristics of a train moving across a seven-span simply supported bridge with the track structure were analyzed for cases of different girder stiffnesses and train speeds. The results demonstrated that the improved RTHS method using the MLCIM effectively represented the TTBI dynamics. The girder stiffness and train speed were shown to substantially influence the responses of the moving train. Further, a ride comfort evaluation confirmed the operational performance of a train on the studied track-bridge structure.

Wind turbines are being used in increasingly complex working environments that generate coupled wind and earthquake effects. Recent projects have tended to construct larger wind turbines to improve efficiency, but this generates more wind-induced vibration. Moreover, different threats are faced by a wind turbine at various stages. During construction, for example, vortex-induced resonance might result in a large lateral displacement of up to 1 metre, making the installation of blades difficult. Meanwhile, during service, the structure of a wind turbine can be damaged by strong gales and sometimes by earthquakes. The present study develops a tuned mass damper, which is designed to mitigate vortex-induced resonance. Shaking-table substructure hybrid tests are conducted to verify the performance of the tuned mass damper for different external loads. The experimental results confirm the effectiveness in terms of suppressing vortex-induced resonance, while the mitigation of the response to wind and earthquakes is limited.