| Since the 21 st century,China’s bridge construction has advanced by leaps and bounds,and large-span bridges across rivers and seas have followed one another,constantly creating a new history of bridge development in the world.With the use of new materials and technologies,the long-span bridge has light weight and low stiffness,and the environment of the sea crossing bridge is complex.The interaction between wind load,wave load and ocean current load will stimulate the bridge structure to produce significant dynamic effect in the wind wave current coupling field,and can stimulate the structure to produce random vibration in a wide frequency band.When the external load period is close to the natural vibration period of the bridge structure,it will cause structural resonance,seriously affect the bridge structure and driving safety,and even the long-time energy input of external load will cause structural dynamic instability and structural damage.At present,cable-stayed bridge structure is the most widely used and maturest bridge structure in mountain crossing,river crossing and sea crossing bridges,the structure’s beam is bent,tower is compressed and cable is tensioned.It has simple structure,clear stress,small self weight and large span,showing significant advantages compared with other long-span bridge structures,but in sea crossing bridges,Under the wind wave current coupling,the structural vibration response of long-span cable-stayed bridge is obvious,which affects the driving safety and structural durability,and shortens the service life.Effective vibration control technology is one of the important means to ensure the performance requirements of long-span cable-stayed bridge in complex external environment.Taking the model of double tower and double cable plane steel box girder cable-stayed bridge as an example,the paper proposes passive control and semi-active control methods based on electromagnetic inertial mass damper（EIMD）.The main research results are as follows:（1）The finite element model of the cable-stayed bridge is established and carrying out the vibration mode analysis.It is found that the large vibration of the cable-stayed bridge under the external interference mainly occurs in the middle of the main beam span,which is the weak point of the whole structure.Therefore,the damper is installed near the middle of the span of the main beam of the cable-stayed bridge structure to control the vibration response of the cable-stayed bridge.（2）The random wind field is simulated by harmonic superposition method,and the spatial fluctuating wind field is simplified into one-dimensional wind field along the transverse and vertical bridge directions.The wave force of large-diameter circular pier column in finite water depth is obtained by using the analytical solution equation.（proposed by Mac Camy and Fuchs in1954）.Different combinations of load cases are used to analyze the interaction between wind,wave and current.The simulation results show that both wind load and current load will have a certain increase effect on the wave height and increase the force of wave on the pier column.（3）According to the mechanical properties and mechanical model of EIMD,the parameters of EIMD are designed;The dynamic differential equation and spatial state equation of cable-stayed bridge structure based on EIMD passive control are established,and the dynamic simulation analysis is carried out in MATLAB.Compared with the dynamic response of cable-stayed bridge structure in uncontrolled state,the results show that the passive control based on EIMD greatly reduces the peak value of dynamic response of cable-stayed bridge structure,and has a significant control effect on the vibration response of cable-stayed bridge structure.（4）As a new type of electromagnetic inertial mass damper,EIMD is not just used in the passive control of the structure.In the paper,by adjusting the external resistance of EIMD,taking the electromagnetic damping force as the semi-active control force,the semi-active control strategy is adopted to make it approach the optimal control force obtained by LQR / LQG algorithm to realize the semi-active control of the structure.The results show that the control effect of LQR algorithm is better than LQG,the displacement and acceleration control of semi-active control is better than the passive control of EIMD,and the speed control effect is slightly worse.（5）Considering the complexity of the marine environment and the difference between the finite element simulation and the real structure,the semi-active control of the traditional control algorithm is used to control the cable-stayed bridge structure,which can not give timely feedback on the problems of variable stiffness and variable mass of the structure for a long time and accurately.To solve these problems,a semi-active control strategy based on fuzzy neural network algorithm is proposed based on EIMD.The results show that although the control force obtained by fuzzy neural network algorithm and LQR algorithm has error,the control effect of fuzzy neural network algorithm can be similar to LQR.Two control algorithms are used to compare the vibration response of cable-stayed bridge structure with variable stiffness,and its robustness is analyzed.The results show that the fuzzy neural network control algorithm has better adaptability and robustness compared with LQR. |
