Structural Health Monitoring of civil structures through FEM high-fidelity modelling

FEM high-fidelity modeling is a useful method for evaluating the dynamic behavior of civil structures and their state of damage through the processing of real-time vibration data in the frame of the general Structural Health Monitoring. The development of reliable digital twin involves the use of high-fidelity models, which must be validated with experimental data. In this study, a prototype of a bridge, composed by a frame structure of steel beams and a slab made in concrete and asphalt, was considered. Two of the main beams have a bolted connection that have been used to simulate a local damage of the structure. FEM models have been validated with experimental data, thus they are able to evaluate both static and dynamic behavior of the bridge and its state of health, referred to benchmark structure. The bridge was degraded considering the breakage of one or more plates of the bolted connection, or an accidental overload capable of creating plastic deformations. The proposed models identify damage of the structure through two different methods: shift of natural frequencies, and evaluation of frequency response of the structure (FRF) at the sensor nodes. The second method is more suitable since the variations of observed variables is more consistent. Therefore, with these models, it is possible to carry out monitoring operations for the predictive maintenance of the structure and defining the limits that the observed variables can undergo in order to still consider the structure suitable for the operating loads.