One-year dynamic monitoring of a steel-concrete composite overpass

Selected results collected in the continuous dynamic monitoring of a 3-span overpass using MEMS accelerometers are reported in the paper. The investigated structure is a steel-concrete composite bridge with a trapezoidal box girder of variable height and curved cross-beams, so that the overall geometry is rather complex. The overpass has a total length of 108 m and spans of 30 m + 48 m + 30 m. The paper firstly presents the dynamic characteristics of the structure obtained from preliminary ambient vibration tests. Subsequently, the effects of environmental and operational variability during the continuous monitoring are highlighted, with the temperature significantly affecting all natural frequencies. A clear effect of changing environment is detected for torsion modes as well, whereas no remarkable changes of bending mode shapes are observed.