Research on the Influence Law of Vehicles to the Natural Frequency of Highway Simply Supported Girder Bridges

In dynamical load test of highway simply supported girder bridges, vehicles are usually used to excite bridges. Because the tested natural frequency of a bridge is vehicle-bridge coupled vibration frequency, the vehicle-bridge coupled vibration frequency is determined by both vehicles and bridge dynamic characteristics. Therefore, vehicles have great influence on the tested natural frequency. Numerical simulation method is used in this paper to analyze the influence law of vehicles to the natural frequency of simply supported girder bridges. Modal synthesis analysis method is used to establish a calculation model of three-dimensional space vehicle-bridge coupled vibrations. Vehicle-bridge coupled vibration model is solved using the modal analysis methods. Vehicle-bridge coupled vibration frequency, that is the tested bridge natural frequency, is calculated. By changing vehicle parameters and vehicle positions on bridges of vehicle-bridge coupled vibration model, bridge natural frequency under different vehicle parameters and different vehicle positions on bridges is calculated. So the influence law of vehicles to the natural frequency of highway simply supported girder bridges is known. The results show that vehicle parameters (vehicle body weight, tire weight, suspension rigidity and tire rigidity) and vehicle positions on bridges have influence on natural frequency of simply supported girder bridges, however, influence law and degree is different.