Research On The Nonlinear Vibration Control Of Building Structures

The active and semi-active control of civil engineering structures rely on the accurate mathematical model in designing process. However, the mass, stiffness and damping of large-scale civil engineering structures cannot be determined accurately. Moreover, the structure components can yield and get into the nonlinear phase under seismic load. Inevitably, there are some defects in the controllers which is designed based on the nominal linear system. On the basis of original linear control algorithms, how to consider the impact of parameter perturbation and nonlinearity on vibration control, is a hot issues in the present study. This paper will research the issue on structural vibration control considering nonlinearity and parameter perturbation, includes the following aspects:For the probelem on how to determine the weight matrix coefficient Q and R in the classical linear optimal (LQR) control algorithm, this paper will use genetic algorithm to optimize Q and R. The fitness function of genetic algorithm is definitied, and the global optimal solution of Q and R are obtained. Ultimately, take a frame structure as an example to verify the damping effect of LQR controller based on genetic algorithm on linear elastic structures.The plastic property of reinforced concrete structures is analyzed based on three-linear model considering stiffness degradation. The elastic-plastic structure is controlled using the LQR controller designed in (1), and the results indicate that when the structure come into plastic under rarely occurred earthquak, the controller which designed based on the nominal system is not suitable for nonlinear structures.To make the traditional control algorithm is suitable for vibration control of nonlinear structures, an innovative control algorithm combineing fuzzy controller and LQR controller to control the elastoplastic structures is put forward. By compareing and analysising the time history curve of linear model and elastic-plastic model under different condition, the conclusion is obtained and shows that, under rarely occurred earthquak the fuzzy controller can remedy the effect of nonlinearity on vibration control; nevertheless, under small earthquake excitation nonlinear structures will not enter nonlinear phase, and this moment the fuzzyt controller does not play a role.Nonlinear robust control algorithm is researched in this paper. On the basis of the theoretical derivation, LQR controller and nonlinear robust controller are combined and applied to the structures with nonlinearity and parameter perturbation. The results show that the nonlinear robust controller can overcome the effect of parameter perturbation and nonlinearity simultaneously on vibration control, and can improve the damping ratio. Furthermore, The nonlinear robust controller under small earthquake does not play a role, which further illustrate the accuracy and effectiveness of the proposed control algorithm in this paper.