Traffic Induced Vibrations at Road-Bridge - Experimental and Numerical Analysis

Sammanfattning: In the north-east part of Lund, Sweden, the MAX IV facility is (in the event of writing this thesis) under construction. MAX IV is a synchrotron radiation facility which has a high requirement regarding low vibrations. Within this thesis a nearby road-bridge for the highway E22 was studied using experimental and numerical methods. The aim was to determine the magnitude of the road-bridge influence to the ground vibrations during passages of vehicles and thereby possibly explain the high levels of vibrations which have been measured during occasional events. A finite element model of the road-bridge and surrounding soil was created using the software Abaqus. Material and soil-layering properties were defined according to a database which have been created during previous geotechnical studies. Geometry of the road-bridge was defined according to construction drawings. The model was studied in two types of analysis; a steady-state and a transient analysis. The transient analysis was based on a load-case which was created in CALFEM/MATLAB using a simple standard axle model which was connected to a continuous beam model. A comparison between measurement data and modelling result was made. The comparison showed that the measured and predicted displacements of the road-bridge during a passage of a vehicle were approximately in the same magnitude. Calculation of 1 s RMS levels of the vibration for the transient load-case at a specific point in the ground, identical to a stationary seismometer location, was done. The 1 s RMS value were below 20 nm in all three directions. It was therefore concluded that the suggested transient load-case not could explain the high levels of vibrations(>200 nm 1s RMS > 5 Hz) which had been measured previously. Although the transient load-case approximated the passage of a vehicle fairly well it was concluded that a more refined load-case and model were needed in order to continue the investigation.