Two-Step Finite Element Model Tuning Strategy of a Bridge Subjected to Mining-Triggered Tremors of Various Intensities Based on Experimental Modal Identification

In this paper, a two-step tuning strategy of a finite element (FE) model of a bridge with pot bearings exposed to mining-triggered tremors of various intensities is proposed. In the study, a reinforced concrete bridge 160 m long is considered. Once the modal identification of the bridge was experimentally carried out based on low-energy ambient vibrations, the FE model was tuned by replacing the free-bearing sliding with a Coulomb friction-regularized model. This model of friction split the tangential relative displacement rates between contacting surfaces into a reversible elastic part and irreversible sliding. The elastic microslip (spring-like behavior) prior to macrosliding can be explained by the deformation of asperities (roughness of contacting surfaces on the microscopic scale). The proposed model allows for accurate sliding bearing performance simulation under both low-energy and high-energy mining-induced tremors. In the first step of the FE model tuning strategy, the elastic microslip constant was experimentally estimated based on the modal identification. In the second step, the macro-sliding friction parameter was implemented to address the realistic behavior of the bridge under mining-induced shocks. Finally, the dynamic responses of the bridge to mining-triggered tremors of various intensities were calculated and assessed using the untuned and tuned FE models. The analysis proved that the untuned model was not suitable for dynamic bridge assessment in the case of low-intensity tremors. The stresses obtained for this model turned out to be strongly underestimated. For shocks of higher intensity, frictionless sliding at the bearings gives a relatively good global estimation of the structure performance but undervalues its local response. The analysis also reveals that the tuned Coulomb friction-regularized model allows for the accurate simulation of sliding bearings under both low and high-energy mining-induced tremors.