Abstract Summary
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 bridge including a trapezoidal box girder of variable height and thin-walled cross-beams with curvilinear axis, so that the overall geometry is rather complex. The overpass has a total length of 108 m and spans of 30 + 48 + 30 m length. 22 tri-axial accelerometers were installed along the two sides of the infrastructure, so that 3 cross-sections per span were instrumented (i.e., at quarter spans and midspan); in addition, as the intermediate supports consist of two elastically deformable inclined steel struts, accelerometers were installed also in the cross-sections corresponding to the intermediate supports. After a concise description of the bridge at study, the paper firstly presents the dynamic characteristics of the structure, as evaluated from ambient response data collected in preliminary ambient vibration tests, and the FE model correlation analysis. Subsequently, the paper describes the dynamic monitoring system installed in the bridge and selected results obtained during the first year of monitoring. Several bending and torsion modes are identified, with the temperature significantly affecting all natural frequencies. Moreover, a clear effect of changing environment is detected for torsion modes as well, whereas no remarkable changes of bending mode shapes are detected.
