Abstract
The dynamic characteristics of long-span suspension bridges are complex. The natural vibration frequency is changed with different structural parameters, and the sensitivity to different parameters is different. In order to solve this problem, the spatial model of a long-span suspension bridge was established by using finite element software, and the first 20 natural vibration periods, natural vibration frequencies and vibration modes were analyzed and calculated. The accuracy of the obtained natural vibration frequency data was verified through field tests. Finally, based on the model, the stiffness of structural components is studied by one -factor-at-one-time, and the influence of various variables on the frequency and mode of a certain mode is studied by one-factor-at-one-time method. The results show that different structural parameters have different effects on the vibration frequency. When the stiffness of stiffening girder and main tower is changed, with the increase of stiffness, the variation of frequency mostly presents an upward trend, and the range is large. With the change of the secondary dead load, most of the frequencies decrease first and then tend to be stable. It can be seen from the field test results that the vibration shapes and frequencies measured by numerical simulation and test are close to each other, which can meet the requirements of engineering precision. The stiffness of the main cable and the main tower has a great influence on the modes and periods corresponding to them. The increase of the secondary dead load can reduce the natural vibration frequency of the suspension bridge, but it is not unlimited to increase the secondary dead load to reduce the frequency. The stiffness of the stiffening girder has a great influence on the frequency of the suspension bridge. When the bending stiffness of the stiffening girder increases to 3 times of the original one, the order of vibration modes of the structure will change. The research results can provide references for structural design and dynamic parameter adjustment of long-span suspension bridge.
Highlights
The dynamic characteristics of long-span suspension bridges are complex
In order to study the influence of different structural parameters of long-span suspension bridges on its dynamic characteristics, three important influencing parameters of the influencing factors of dynamic characteristics are extracted to discuss the influence of dynamic characteristics on the natural vibration frequency of the suspension bridge
In order to analyze the influence of the stiffness of the main tower of the suspension bridge on the dynamic characteristics of the suspension bridge, the analysis was carried out by changing the stiffness of the main tower, and the previous method was still adopted on the basis of the original design stiffness
Summary
The dynamic characteristics of long-span suspension bridges are complex. When the structure is excited by external dynamics, the vibration modes in all directions in space can generally be divided into four types: horizontal, vertical, longitudinal, and torsion. One is how to obtain the low-frequency dynamic characteristics of the real bridge, how to verify each other between the field tests and the numerical simulations; the other is how the structure parameters of the bridge affect the frequency and how to analyze the coupled vibration under environmental excitation. There are few studies on the comparison of the dynamic characteristics obtained from the field test and numerical simulation of the long-span suspension bridge and the influence of the coupling of multiple parameters on the natural vibration period of the suspension bridge. The vibration mode, natural vibration frequency, and damping parameters of the background bridge obtained through theoretical analysis can characterize the actual state of the bridge structure. Vibration direction vibration mode natural vibration frequency /Hz Theoretical value Measured value error /%
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