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

Abstract

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.

Advanced Model of Spatiotemporal Mining-Induced Kinematic Excitation for Multiple-Support Bridges Based on the Regional Seismicity Characteristics

“…Such a simplification is not appropriate since, due to the very low level of ambient vibration used with the OMA techniques, sliding in the pot bearings was prevented by frictional forces. However, as it was proved in the work [51], tuning the FE model is not required in case of excitation by a strong mining tremor, which is strong enough to defeat frictional forces in the bearings immediately; thus, the numerically obtained dynamic performance of the structure is not affected by the assumption of frictionless sliding at bearings. The natural frequencies determined numerically and experimentally are compared in Table 2.…”

“…The experimental and numerical evaluation of the dynamic characteristics of the bridge were presented in detail in the previous authors' work [51]. The locations of the measurement points on the half of the bridge are presented in Figure 7.…”

“…Again, the experimental evaluation of the damping properties of the bridge was presented in detail in the work [51]. The estimation was based on the discrete experimental data acquired during a jumping test.…”

Archives of Mining Sciences

“…By maximising the product of ordinates for the set of eigenmodes, simplified quantitative information was obtained for the response of the structure for the eigenmode periods in the individual segments. The set of these values, determined for each of the segments of the conveyor bridge under analysis, made it possible to indicate the segment with the most intense dynamic response for the assumed dynamic characteristics of the terrain in the form of adopted standard acceleration response spectra (7) and (8).…”

“…They increase in time and usually cover a large area of terrain. The second type of negative impact is the so-called mining tremors [8,9]. They are dynamic and manifest on the ground surface in the form of ground vibrations induced by sudden relief of the rock mass.…”