Resumo em Inglês:

Abstract The experimental study investigates design parameters affecting the fatigue performance of bolted flange connections using accelerated laboratory tests at 60–70% of static capacity. Constant-amplitude loading R = 2 Hz was applied to large-diameter high-strength bolts (M36 and M39, Grade 8.8), considering variations in flange material S355 and SAE 1045, bolt size, and loading 5 mm eccentricity. M39 bolts showed statistically significant longer fatigue life than M36 bolts 8,579 vs. 5,395 cycles, p = 0.023. A 5 mm loading eccentricity reduced fatigue performance due to induced bending effects. While both flange materials showed comparable fatigue lives, the higher ductility of S355 provided improved damage progression control. Dynamic stiffness monitoring identified a three-stage degradation process, with critical reductions in final fatigue stages, indicating potential for early failure detection. Although accelerated tests do not predict absolute service life, results provide relative performance rankings and practical guidance for bolt selection and design of large-scale bolted structures, particularly wind turbine towers.

Resumo em Inglês:

Abstract This study investigates the down-aisle seismic performance of a full-scale 3D cold-formed steel rack system using shaking table tests. The rack system was tested using scaled Northridge earthquake records, and the dynamic responses were evaluated during the test. The results demonstrated that the rack response remained essentially elastic up to approximately 50% of the Northridge intensity, beyond which pronounced inelastic behavior, approximately 50% stiffness degradation, and permanent drifts were observed. The experimental results were validated using an FE analysis, with substantial agreement in the elastic-to-mildly inelastic range, with similarity ratios of approximately 80%. However, differences were observed in the response values at the higher excitation intensities due to the high pallet sliding and connection slip during the test, which could not be accurately reflected in the FE model. It was observed that pallet sliding and connection friction, rather than member strength alone, governed the response under strong shaking and should be explicitly considered in advanced numerical models and in the seismic assessment of steel racks.