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A new control strategy based on modal energy criterion is proposed to demonstrate the effectiveness of the control system in reducing structural earthquake responses. The modal control algorithm combining LQR (linear quadratic regulator) control algorithm is adopted in the discrete time-history analysis. The various modal energy forms are derived by definition of the generalized absolute displacement vector. A preliminary numerical study of the effectiveness of this control strategy is carried out on a 20-storey framed steel structural model. The controlled performance of the model is studied from the perspectives of both response and modal energy. Results show that the modal energy-based control strategy is very effective in reducing structural responses as well as in consuming a large amount of modal energy, while augmentation of additional generalized control force corresponding to the modes that contain little modal energy is unnecessary, as it does little help to improve the controlled structural performance.

One of the challenges confronting structural engineers in structural control is to find more efficient control algorithms to ensure better and more reliable control results to protect structures against the damaging effects of destructive environmental forces. In this paper, a simple control algorithm, namely the Predictive Instantaneous Optimal Control (PIOC) algorithm, is proposed by introducing a new state space form. Different from the classical ground acceleration‐based control algorithms, this new control algorithm uses earthquake ground velocity as the input. Since the earthquake ground velocity is not at high frequency as compared with the ground acceleration, it can be predicted at certain time steps beforehand in real‐time domain with higher accuracy. This ensures the synchronous execution of the proposed PIOC algorithm with real‐time application of the control force. To capture the damaging effects during earthquake ground motions, the force analogy method is used to characterize structures responding in the inelastic domain. Numerical studies are performed to compare the structural response with and without control using both single degree of freedom and multi‐degree of freedom structural models. Results show that the PIOC algorithm is effective in reducing the structural response under earthquake excitation. Copyright © 2006 John Wiley & Sons, Ltd.

This study examines the use of fiber reinforced polymer (FRP) rebars as an alternative to steel rebars in externally prestressed concrete (EPC) continuous beams to alleviate the corrosion problem. To the best of the authors’ knowledge, this is the first study on continuous EPC beams with FRP rebars, taking into account the pattern of loading. By utilizing an experimentally verified computer model, numerical assessments are conducted on two-span EPC beams with carbon FRP (CFRP), glass FRP (GFRP) or steel rebars, subjected to symmetrical or unsymmetrical loading. The results show that providing a minimum FRP rebars is more effective in alleviating the cracking concentration than providing steel rebars. At ultimate, unsymmetrical loading leads to greater deflection in the critical midspan but lower tendon stress than symmetrical loading, while the deflection or stress difference highly depends on the type of rebars (FRP/steel). Several design codes for calculating the ultimate tendon stress are evaluated. Practical equations are proposed to predict the ultimate tendon stress in continuous EPC beams with FRP/steel rebars. The proposed equations exhibit much better predictions than the design codes.