Study On Damage Identification Of Cable Stayed Bridge Based On Wavelet Packet And Support Vector Machines

Because of the advantages of strong spanning ability,simple and beautiful structural form,good mechanical properties and economic indicators,cable-stayed bridges have been widely used.With the development of cable-stayed bridges,performing the health monitoring and damage identification of cable-stayed bridges in time is extremely important for the safe operation and maintenance of the bridge,and it is great significance to the prevention of accidents and the safety of life and property.Therefore,in this thesis the study on damage identification of cable-stayed bridge based on wavelet packet analysis and support vector machine have been done.(1)The damage identification index of wavelet packet energy change rate is deduced theoretically,and the feasibility of this index for the damage identification of cable-stayed bridge main girder and stayed cable is proved by numerical simulation.(2)A damage identification method based on wavelet packet analysis and support vector machine is proposed.The laboratory model bridge is used to carry out numerical simulation.The result shows that this method can accurately identify the position and degree of linear damage of the cable-stayed bridge main girder and stayed cable.On this basis,the influence on the position recognition result by the position and number of input vectors have been done.It is found that the position of the input vector has little influence on the damage identification result of stayed cable,and has a greater influence on the cable-stayed bridge main girder.With the increasing of the number of input vectors,the recognition accuracy of the cable-stayed bridge main girder and stayed cable gradually increase.(3)Using the method of damage identification based on wavelet packet analysis and support vector machine,the nonlinear damage identification of the cable-stayed bridge main girder and stayed cable is discussed.It is found that this method can be used to detect the nonlinear damage,and it is found that the recognition accuracy of nonlinear damage is slightly lower than that of linear damage recognition.(4)The influence of noise on this method is analyzed.The result shows that damage misjudgment will be produce with the increasing of the noise level,and the effect of noise on identification result of the cable-stayed bridge main girder is stronger than that of the stayed cable.