No abstract

When an earthquake occurs, it can strongly shake high-speed railway bridges. Consequently, the dynamic displacement of the rail on the bridge may exceed the allowable standard. However, few studies have evaluated the probability of rail displacement exceeding the allowable standard, compared to the rich variety of research on the vulnerability of other components of the high-speed railway track-bridge system or other structures. In this paper, incremental dynamic analysis (IDA) is applied to calculate the exceeding probability of rail displacement under different earthquake excitations. A finite element model (FEM) of a high-speed railway track-bridge system is established, which consists of a finite length CRTS II ballastless track laid on a five-span simply supported girder bridge. Records from five stations in the PEER NGA−West2 strong ground motion dataset are selected as seismic excitation. Based on the simulation, the characteristics of the vertical displacement of the rail under different seismic excitations are investigated, and the probability of the vertical displacement of the rail exceeding the allowable standard is calculated using IDA. The results show that: (1) the vertical displacement of the rail above the abutment is significantly smaller than that above other parts of the bridge; (2) the vertical irregularity of the rail caused by earthquakes has a wavelength close to the length of a simply supported girder; (3) under some excitations, two bumps are observed in the Fourier displacement spectrum in the frequency range of 1.3–2.5 Hz and 10–12 Hz, respectively, which may indicate the resonance of the model to the excitation; and (4) the vertical displacement amplitude probability of the rail exceeding 2 mm is 44%, 89%, and 99% when PGA = 0.01 g, 0.20 g, and 0.40 g, respectively. The exceeding probability of the rail above the mid-span is larger than that above other parts of the bridge. Within the mid-span, the exceeding probability of the rail is the largest above the center of the bridge.

A coupling dynamic model of a subway train and an embedded track is established to study the safety limits of track irregularities. The simulated vehicle system was a 74-degrees of freedom multi-rigid body model, and the rail was a Timoshenko beam. The slab was a three-dimensional solid finite element model. The sensitive wavelength irregularity was first studied, and then the safety limit of the sensitive wavelength was analyzed. The wheel-rail lateral force exhibited a substantial effect on the track alignment and gauge irregularity safety limit. The wheel-rail vertical force and the rate of wheel load reduction significantly affected the height and cross-level irregularity safety limit. The results demonstrate that the safety limits of the alignment, gauge, height, and cross-level embedded track geometric irregularity are 5.3 mm, [− 10.5, 8] mm, 5.6 mm, and 6 mm, respectively.