SIMULATION OF DYNAMIC LOAD FOR BRIDGES

This paper deals with the analysis of dynamic loads in bridges. Models are developed for trucks, road surface (roughness) and the bridge. The statistical parameters are based on the results of surveys, tests and analysis. Truck parameters include the body (mass), suspensions, and tires. Road profiles are simulated using stochastic processes (power spectral density function). A bridge is treated as a prismatic beam. The Monte Carlo method is used to simulate the traffic on the bridge. Random variables include the truck type, total weight, axle distances, and speed. Calculations are carried out for steel and prestressed concrete girder bridges. The dynamic load factors for a bridge design code are calculated based on the 75 year mean maximum loads. The analysis is performed for single trucks and for two trucks (side by side). Dynamic loads are lower for heavier trucks and also lower for two trucks. The calculated static and dynamic deflections are presented in tables and graphs as a function of gross vehicle weight, span and axle distance. Simulated deflections indicate that the dynamic component is not correlated with the static component. Therefore, the dynamic loads are lower for heavier truck. It is also found that the dynamic loads for two trucks are lower than for single trucks.