Research On Vibration Characteristics Of Cables Subjected To Periodic Support Excitation

This paper studies the vibration characteristics of stay cables subjected to periodic support excitation,and provides theoretical basis for the parameter design and vibration control measures of stay cables.The main research contents are as follows:(1)The cable model is established under the plane local coordinate system,and the finite element modeling method of the cable structure is deduced.The assembly of the stiffness matrix consists of two steps.The first step is coordinating the local unit model.The second step is extracting the stiffness elements into the structural matrix.The method can improve the modeling logic and optimize the modeling progress when numerically simulate complex structures like cable-stayed bridges.Numerical examples show that the modeling method is simple and reliable,and it is suitable for model building of multiple combined structures.(2)The model is uniform for the same element.In the process of coordinate transformation of the model,selecting different node connection relationships will result in inconsistent conversion results.However,in the process of global stiffness assembly,it is also necessary to extract the coordinate elements after the coordinate transformation into the whole structure according to the correspondence relationship of the displacement components of the nodes,so as to realize the establishment of the final model.It is verified that the change of the joint order of the nodes does not affect the final modeling results.(3)In order to modify the dynamic structure of cable-stayed bridge,a method for structure damage identification based on element stiffness matrix decomposition is proposed.A new element stiffness matrix form is obtained by decomposing and reconstructing the element element stiffness matrix.The measured node displacement information is brought into the analysis model to obtain the section parameters of each component in the structure,and analysis of the damage location and damage degree for the component is realized.A method based on stiffness matrix decomposition for cable force identification is proposed,which can identify the cabletension of cable-stayed bridge model.The method has high recognition accuracy and can provide reference for the design of cable-stayed model.(4)By numerical simulating the cable,it is found that the established model is very reliable,and the model is suitable for the parameter design of the stay cable.Through the natural vibration mode of the stay cable,it is found that the frequency of the first few steps is low.The diagonal cable can generate a large resonance subjected to periodic support excitation,which seriously affects the safety performance of the bridge.The amplitude of the cable can be effectively controlled when measures are taken to increase the cable damping.(5)Dynamic models are established based on different vibration modes of cable.The forced resonance and parametric resonance of the cable subjected to periodic harmonic support excitation is analyzed,and the main resonance causes the larger vibration of the cable is determined.The natural frequency of the whole bridge and the natural frequency of the cable is compared by focusing on the cable-stayed bridge structure in actual engineering,it is found that the most unfavorable vibration form of the cable-stayed bridge is analyzed subjected to external excitation such as wind-rain or vehicle.The dynamic response time history monitored in the field is used to further analyze the response time history curve of the cable under the action of earthquake.The results show that the response time of the bridge deck under earthquake action is dominated by low frequency components,which cause large vibration of the cable.It can endanger the safety of the cable-stayed bridge.This paper has engineering practical value and scientific significance for the development of cable-stayed bridge technology.