Natural Frequency for Torsional Vibration of Steel I-girders with Cross-beam Bracings

摘要

In this study,analytical solution for natural frequency and stiffness requirement for torsional vibration of I-girders with intermediate bracings is derived and a series of parametric study is conducted. Natural frequency is essential in formation to perform the dynamic analysis. It is crucial to thoroughly understand the natural frequency to study noise and vibration induced by cars or trains which are the mayor disadvantages of the steel I-girder bridge. Firstly, the natural frequencies for torsional vibration and required stiffness for torsional bracings are derived by using La grange's equation in this study. Derived equations have simple closed form and it can be applied to arbitrary number of bracing points. The proposed equations are then verified by comparing with the results of finite element analysis. From the results,it can be found that proposed equations provide good prediction of natural frequency for torsional vibration of I-girder with intermediate bracings. The derived equations applied to twin I-girder system as an example of practical civil engineering application. Finally, the effects of number of bracing points and total torsional stiffness on torsional vibration are discussed based on the analysis results of twin I-girder system.