Urban rail transit (URT) viaducts are subjected to long-term train-induced vibration, yet conventional train-bridge dynamic analyses rarely reveal how the parameters of bridge bearing control vibration transmission from the perspective of wave propagation. This study proposes a band-gap-analysis-based design method for vibration-isolation bearings in periodic URT viaducts. A train-track-bridge dynamic interaction program is first used to obtain the wheel-rail interaction forces, which are then introduced into a frequency-domain analytical model of a periodic bridge established based on Bloch’s theorem and the Fourier transform. The model is verified against an analytical solution for a periodic simply supported beam bridge. Taking the viaduct of Beijing Metro Line 13 as a case study, the characteristic wave modes, complex-wavenumber characteristics, and attenuation curves are analyzed to select the vertical stiffness and damping of the bearings. The results show that reducing the bearing vertical stiffness and increasing the equivalent damping can enhance spatial wave attenuation and reduce vibration transmission between spans. For the investigated viaduct, the suitable bearing parameters are identified as a vertical stiffness of 1.0 × 10 8 N/m and an equivalent damping coefficient of 6.0 × 10 6 N·s/m. Frequency- and time-domain comparisons further confirm that the recommended bearing system suppresses high-energy vibration components while satisfying displacement limits. The proposed method provides a theoretical and practical basis for vibration-isolation design of periodic urban rail transit viaducts.
To investigate the progressive collapse resistance of intersected latticed threedimensional beam system(ILTDBS) reticulated mega-structures, a comprehensive numerical simulation study was conducted. The dynamic responses and collapse mechanisms of the ILTDBS reticulated mega-structure under various impact loading scenarios were systematically examined. The finite element modeling approach was first validated by reproducing a previously reported drop-weight impact test and comparing the numerical predictions with the experimental data. Subsequently, a refined finite element model incorporating cumulative member damage was developed in LS-DYNA using an explicit time-integration scheme. The model was employed to investigate the structural failure modes, collapse mechanisms, and transfer and dissipation of impact energy. On this basis, several impact-resistant strengthening strategies were proposed. The results indicate that the presence of the substructure provides substantial support to the main truss, thereby significantly enhancing the deformation capacity and impact resistance of the overall structure. Three primary failure modes were identified: slight structural damage, plastic spreading of the truss, and overall collapse. In the first two modes, redistribution of internal forces was observed, whereas overall collapse was characterized by the formation of plastic hinges at the ends of the truss beams. A critical relationship was found between the structural failure mode and the energy absorbed by the trussed arch. The absorbed energy was positively correlated with both the impact mass and impact velocity. Overall structural collapse can be effectively controlled through impact-resistant strengthening measures, including conceptual design optimization, reinforcement of critical members, and local addition of braces to restrain vulnerable regions. Recommended correlation coefficients are also provided to guide practical design.
Perovskite materials have attracted considerable attention in recent years in the development of advanced multifunctional structures due to their excellent multi-physical properties. This paper investigates the static and dynamic behaviors of annular perovskite plates under combined light, electric and mechanical fields. Based on the first-order shear deformation theory, the multi-physics stress-strain constitutive model taking into consideration the geometric nonlinearity and effects of photostriction, thermal expansion, and electrostriction properties of perovskite is developed in a cylindrical coordinate system. Subsequently, the nonlinear partial differential governing equations are formulated for annular perovskite plates which are then solved numerically by the general differential quadrature method to determine their nonlinear deflections and vibration characteristics. Parametric analyses are conducted to evaluate the effects of combined multi-physics fields on the bending, free vibration, and dynamic response of annular perovskite plates. Numerical results reveal that the photothermal effect cannot be neglected for the static and dynamic analysis of perovskite-based structures. The combined light and electric fields significantly soften the plate, thereby increasing the nonlinear static and dynamic deformations of the annular plate under external mechanical loads. In addition, the simply-supported annular plate is more sensitive to combined external fields than the clamped-clamped one. These observations offer valuable insights for optimizing perovskite-based plate design with high performance.
To reduce stay-cable vibration caused by a uniform transverse load, support-end motion and their combined action, this study proposes a lever-type time-delayed nonlinear energy sink (TDNES) that integrates a lever mechanism, an NES and delayed velocity feedback. The lever simultaneously modifies the absorber-base motion and the equivalent control force applied to the cable, while the feedback gain and delay provide adjustable control parameters. A coupled dynamic model is established, and Galerkin truncation is used to derive reduced equations for the uniform-load, end-load and dual-load cases. The delayed system is linearized, and its characteristic equation is used to determine the Hopf stability boundary. The harmonic balance method and direct time integration are employed to calculate the frequency and steady-state responses. Parameter-plane, reduction-efficiency and energy analyses are conducted to examine the effects of the lever coefficient, feedback gain and delay and to compare parameter selection under the three excitation routes. Initial-condition scans further assess the low-response initial perturbation tolerance of the proposed TDNES. The results also show that the cable response under dual excitation varies with the relative input phase.
Cross-sea single-level rail-cum-road bridges are simultaneously subjected to traffic, strong winds, and waves, and their coupled vibration directly affects bridge serviceability and vehicle safety. To clarify the dynamic interaction mechanism of the wind–wave–road vehicle–train–bridge system, this study develops a refined time-varying coupled model using the Jinhai Bridge, the world’s first single-level rail-cum-road multi-tower cable-stayed bridge, as a case study. Road vehicles, trains, tracks, and the bridge are modeled as an integrated system through dynamic interaction matrices; wind tunnel tests are conducted to determine the aerodynamic coefficients of six typical vehicle models under the combined effects of the bridge and trains; and irregular wind and wave fields are simulated for multi-case dynamic analyses. The results show that the lateral vibration of the main girder is governed mainly by wind loads, whereas vertical and torsional vibrations are dominated by vehicle loads. Under the investigated cases, wave loading makes only a limited contribution to the response at the selected main-girder observation point. For the analyzed random-traffic realization, frequency proximity and unfavorable spatial coincidence among the train, a heavy truck, and the local bridge response produce a local amplification, indicating a potential bridge-mediated interaction mechanism; light vehicles are less affected. High train speeds may cause the windward wheel load reduction ratio to exceed the safety limit, whereas low train speeds can amplify bridge vibration and reduce road-vehicle safety and comfort.
