Diagnosis of railway bridge scour by natural vibration frequencies

Abstract

Existing methods for detecting of railway bridge scour do not exclude the occurrence of unforeseen emergencies. This is due to the impossibility of performing work during the flood period, as well as the rather rare frequency of depth measurements on small and medium-sized bridges. Therefore, the aim of the study is to improve the operational reliability of railway bridges by improving the method for detecting bridge scour by the natural vibration frequencies.
In the course of the study, in order to establish the actual dynamic nature of the operation of the railway bridge piers, full-scale measurements of the natural vibration frequencies were performed. The vibration measurement carried out for 30 supports of various designs at the actual depth of foundations. The measurements used the multifunctional measuring system “Tensor MS”. Computational studies completed to predict changes in the fixed natural vibration frequencies during the development of bridge scour. The developed mathematical models of piers take into account the compatibility of their work with superstructures and interaction with base soils. In this research, nature of the work of the carriages with free vibrations of the structure is estimated. Also, the required degree of detail in the modeling of structures is established to obtain data corresponding to the actually recorded ones. The assessment of the conformity of the model to the actual dynamic nature of the operation of the supports is made by the value of the design coefficient. After verification of the calculation models for all objects of study, the calculation and experimental dependences of the natural vibration frequencies of the piers on the depth of bridge scour are revealed.
The introduction of an improved method for monitoring soil erosion of railway bridge scours will improve the operational reliability of railway bridges, as well as reduce the cost of carrying out work to control the depth of bridge scours.