Vehicle Response To Identify The Natural Frequency Of The Bridge

The natural frequency is one of the most important dynamic characteristics of the bridge, and a key index in the model verification, parameters and damage identification. At present, the main method of. extracting the natural frequencies of the bridge is to obtain its dynamic response, in recent years; a new approach is proposed to extract the natural frequencies by installing the sensors on the vehicle in order to obtain the dynamic response of the bridge excited by the passing vehicle. Compared with the traditional methods, this new method is preferred because of its higher safety and removability without laying out sensors on the bridge or obstructing the traffic. Based on this, in this paper, the theoretical and experimental study on the new method of extracting the natural frequencies of the bridge is presented. In details, the following aspects are investigated:1. The traditional methods of extracting the natural frequencies of the bridge are introduced, and the new method of obtaining the dynamic response of a passing vehicle to extract the natural frequencies is deduced following with relevant parameters analysis.2. The numerical methods of vehicle-bridge coupling vibration are listed out. The single-degree-of-freedom sprung mass model and the four-degree-of-freedom vehicle model are built up separately considering the surface roughness with the finite element program which is based on MATLAB compiled.3. According to the results of the finite element analysis, the feasibility of the new method is verified numerically. The influences of the vehicle passing speed, vehicle damping, damping ratio of the bridge, vehicle/bridge mass ratio and the surface roughness are studied. Then the feasibility of extracting the first two order frequencies of the bridge is demonstrated using the results of the four-degree-of-freedom vehicle model. 4. Additionally, the feasibility of the new method is verified experimentally by comparing it with the ambient excitation method, and finally the influences of the passing speed of the vehicle and the surface roughness are analyzed.