Dynamic behaviour of railway poles built on bridges under train passage in high-speed railways and a simple evaluation method

Abstract

There have been studies on increased dynamic response of bridges for high-speed railways (HSRs) and damage to the overhead contact line system (OCS), including wires supported by railway poles placed on resonant bridges. However, the dynamic behavior of the poles installed on bridges under train passages, which is considerably related to the damage to the OCS, has not been systematically examined. This study aims to examine the dynamic behaviour of poles installed on bridges and provide a simple calculation method or guidelines for bridge design and OCS maintenance considering pole vibration. First, a field test of a HSR bridge with poles was conducted, and numerical simulations using a finite element model of pole and bridge were validated. Next, a parametric study using the validated numerical model was conducted. The results demonstrated that the multiple resonances observed when the excitation frequency of travelling train matches the bridge and pole frequencies can cause dominant vibration of the poles built at the bridge edge, thus posing a risk of OCS wire fatigue. In addition to the understanding of the basic dynamic behavior, a simple calculation approach based on a theoretical model considering the interaction between the bridge and poles installed at the bridge edge is developed for practical use. The proposed model clarifies train-induced pole top displacements with standard bridge and pole specifications in Japanese HSRs. Using the bridge/pole frequency ratio and bridge span length, the results are presented in the form of a pole response map that can be used to calculate the pole top displacement. Finally, an example of bridge frequency guidelines is provided for extracting and evaluating poles that may require attention for maintaining the OCSs.