The effects of surface roughness and vehicle suspension type on highway bridge dynamics

This study focuses on the effects of surface roughness and vehicle suspension type on the dynamic responses of highway bridges.; Three Swiss highway bridges and one Australian highway bridge tested in the OECD DIVINE project are chosen for the study on the basis of their natural frequencies. These bridges have span lengths ranging from 9 m to 70 m and fundamental natural frequencies varying from 1.6 Hz to 11 Hz, which cover the frequency range for vehicle body-bounce and axle-hop vibration modes.; The bridges are modelled as beams to obtain their modal properties. The bridge models are validated by comparing the predicted bridge modal properties with those measured in the DIVINE project, and also by comparing calculated bridge responses at certain speeds with the responses obtained from DIVINE tests. Good agreement is found and the validation is satisfactory.; The measured road profiles of the four bridges are used in the study. Smoother and rougher road profiles based on the measured ones are also created to investigate the effect of road roughness. Bridge responses are predicted using a convolution method by combining bridge modal properties with vehicle wheel forces generated by the non-linear air-sprung and leaf-sprung vehicle models. The study is conducted at speeds of 10 to 25 m/s. The effect of surface roughness, vehicle suspension type, and vehicle speed is assessed using the quantity: dynamic increment of bridge responses. It was found that air-sprung vehicles cause less bridge dynamic responses than steel-sprung vehicles, especially in rough surface conditions.