A Theoretical Model to Identify the Fundamental Frequency of Simply Supported Girders from a Passing Heavy Vehicle

Abstract

This paper discusses the influence of vehicle parameters on the identification accuracy of bridge fundamental frequency from a passing vehicle and validates such influence through laboratory tests. In the process of theoretical derivation, the interaction between a vehicle and bridge is no longer ignored to uncouple the equation group and the stepwise integration method is used to solve the equation group. Key parameters such as the vehicle speed αv, vehicle-to-bridge mass ratio αmv, and frequency ratio μ1, are dimensionless. Based on the simplified vehicle-to-bridge system model, the numerical analysis method is used to analyze their influence on the identified bridge frequency. Through parameter analysis, it is found that the vehicle-to-bridge mass ratio and vehicle speed have a great impact on the patterns of identified bridge frequency; and when the vehicle frequency is greater than or less than the bridge frequency, the identified bridge frequency exhibits different patterns. The bridge frequency deviation rate can be greater than 20% when the vehicle speed and vehicle-to-bridge mass ratio increases. In order to ensure the accuracy of bridge frequency identification, it is recommended that the vehicle-bridge mass ratio should not exceed 10%. Besides, appropriately increasing the vehicle-to-bridge mass ratio will increase the probability of accurately identifying the bridge frequency under certain conditions. In addition, a novel frequency extraction method was proposed to more accurately filter out the frequency from the vehicle acceleration spectrum.

Keywords

• bridge
• fundamental frequency
• vehicle mass
• frequency deviation
• vehicle-bridge interaction
• laboratory test