Dynamic behaviour of soil-steel composite bridges for high-speed railways

This report deals with the dynamic behavior of corrugated steel culverts underrailways. The main objective is to investigate the feasibility of these structures forhigh-speed trains. A combination of experimental testing and numerical simulationsis presented. Experimental testing is reported for three bridges, all built for conventional railways.The main novelty of the work is a method for forced vibration tests. Thisis performed using a 50 kN load actuator from inside the culverts. The forcedvibration tests enables experimental estimates of the frequency response functionsat all sensor locations, both in the culvert and the adjacent track area. For thetested bridges, the first resonance frequency is in the range of 15-20 Hz and thedamping is estimated to 4-8%. Tests with increased load amplitude generally showa decrease in natural frequency but increase in damping, possibly due to nonlineareffects of the soil-structure system. Numerical models have been developed, mainly focusing on the largest of the studiedbridges. The parameters of the numerical model is fitted using a model updatingalgorithm together with the experimental data. A full 3D model of the bridgeis rather computationally demanding, especially when simulating passing trains.Therefore, a simplified 1D track model with modified parameters has been developed.Relatively good agreement is found between the 1D and 3D model. Bothmodels show that the studied bridge is likely to fulfill the dynamic requirementsfor high-speed trains, according to EN 1990. The 3D model also shows relatively good agreement with experimental data of realtrain passages. At the centre crown point, the model somewhat underestimate theresponse.QC 20200910