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Picture of a white high bridge, taken from below, surrounded by green hills and blue sky

Traffic vibrations of road bridges

Construction work on existing bridges often has to take place while traffic is maintained. In particular, hardening structural elements such as concrete are exposed to traffic-induced vibrations when bridges are widened or construction joints are closed, which can cause lasting damage to the structure during the critical hardening phase. Whether or not the strength is reduced by this effect depends primarily on the amplitude of the vibration velocity that occurs.

AIT has investigated influences on the magnitude of traffic-induced vibrations of a real bridge structure. By means of dynamic time-course passage calculations, those parameters that have the greatest influence on the bridge vibrations were identified by varying the speed of travel, vehicle mass and road profile. The FEM simulation used real road profile data, which were collected with the measuring vehicle RoadSTAR by high-resolution laser scanning of the relevant lanes. The dynamic structural properties were verified by vibration measurements.

While the deflections and strains of the structure are mainly influenced by the vehicle mass, the dynamic vibration velocities primarily determine the road profile. The occurring vibration velocities were compared with a limit value, which should not lead to any impairment of the young concrete. The results provide a basis for decisions on suitable measures to avoid harmful vibrations during the critical hardening phase of the young concrete in the connecting joint.