To improve the energy dissipation capacity of rubber isolation bearings, it is important to find a new rubber material with good applicability and high damping properties. Two types of blends were prepared using nitrile rubber (NBR), brominated butyl rubber (BIIR) and ethylene-vinyl acetate copolymer (EVA): NBR/BIIR and NBR/BIIR/EVA. The vulcanization, mechanical and damping properties of the blends were analyzed. The results show that both blends exhibit excellent vulcanization plateaus and mechanical properties. For NBR/BIIR, as the BIIR content increases, the complementary effects of NBR and BIIR afforded by blending are enhanced. Two damping peaks appeared in the tanδ-T curve and shifted toward lower and higher temperatures, respectively, which clearly widened the effective damping temperature range. However, the damping value in the valley of the tanδ-T curve was as low as 0.39. For NBR/BIIR/EVA, the addition of EVA greatly increased damping in the valley of the tanδ-T curve to approximately 0.54. EVA was observed to be the optimal polymer for improving the compatibility of the NBR/BIIR blend. Moreover, hot air thermal aging tests showed that both blends demonstrated good stability.

In this paper, the dynamic response of a simply supported beam subjected to a moving load is reinvestigated. Based on a new beam theory, slope inertia-based Timoshenko (SIBT), the governing equations of motion of the beam are derived. An analytical solution is presented by using a coupled Fourier and Laplace–Carson integral transformation method. The finite element solution is also developed and compared with the analytical solution. Then, a comparative study of three beam models based on the SIBT, Euler–Bernoulli and Timoshenko, subjected to a moving load, is presented. The results show that for slender beams, the dynamic responses calculated by the three theories have marginal differences. However, as the ratio of the cross-sectional size to beam length increases, the dynamic magnification factors for the mid-span displacement obtained by the SIBT and Timoshenko beams become larger than those obtained by the Euler–Bernoulli beams. Furthermore, until the ratio is greater than 1/3, the difference between the calculated results of the SIBT and Timoshenko beams becomes apparent.

As a primary load-bearing component, accurately predicting the bearing capacity of concrete-filled rectangular steel tube (CFRST) members is an essential prerequisite for ensuring structural safety. Machine learning methods are employed to model and predict the axial load bearing capacity of CFRST columns. A test database containing 1119 members is established, and the input parameters of the machine learning model are determined using a combination of data preprocessing and correlation analysis. Four machine learning algorithms, namely Lasso, ANN, RF, and XGBoost, are selected to build the prediction models for axial load bearing capacity, and a comparative analysis of their predictive performance is conducted. The feature importance analysis is performed using the SHAP method. The results indicate that the model based on the XGBoost algorithm achieves the highest prediction accuracy. Through comparison with six existing calculation methods in domestic and international codes, the reliability of its predictive performance is verified.

Concrete prepared using Gobi sand and gravel instead of ordinary sand and gravel is referred to as Gobi concrete. In order to explore the effect of fibers on the frost resistance of Gobi concrete, as well as to enhance the service life of Gobi aggregate concrete in Northwest China, experiments were conducted with fiber types (polypropylene fibers, basalt fibers, polypropylene–basalt fibers) and fiber volume fractions (0%, 0.1%, 0.2%, 0.3%) as variable parameters. This study investigated the surface morphology, mass loss rate, and relative dynamic elastic modulus of fiber-reinforced Gobi concrete after different freeze–thaw cycles (0, 25, 50, 75, 100). Corresponding frost damage deterioration models were proposed. The results indicate that fibers have a favorable effect on the anti-peeling performance, mass loss rate, and dynamic elastic modulus of Gobi aggregate concrete. The improvement levels of different fiber types are in the following order: 0.1% basalt-polypropylene fibers, 0.2% polypropylene fibers, and 0.3% basalt fibers. Compared to Gobi concrete exposed to natural environmental conditions, the freeze–thaw cycle numbers increased by 343, 79, and 69 times, respectively. A quadratic polynomial damage model for fiber-reinforced Gobi concrete, using relative dynamic elastic modulus as the damage variable, was established and demonstrated good predictive performance.

On account of the influence of the discontinuity of CRTS II ballastless track slabs and the discrete support of track pads on the high-speed rail vehicle-ballastless track system, a vibration analysis calculation model of the ballastless track-vehicle coupling system was established on the basis of the moving unit method. The dynamic response of the system at different travel speeds and with and without consideration of the track plate discontinuities was investigated. The effect of the random process discontinuity on the dynamic response of the steel rails was analyzed by Fourier inverse transform on the high and low discontinuity spectra of ballastless rails on China’s high-speed rail. We also generated time domain samples of the track discontinuity corresponding to the three percentile spectra. The results show that the dynamic response of the track structure increases with the speed of the train under the condition of track unevenness, with the dynamic response of the steel rail being the most significant, while the dynamic response of the track slab and concrete foundation decreases step by step compared with that of the steel rail; the discontinuity of the track slab has a low impact on the vertical acceleration of the vehicle and does not affect the smoothness of the train; the magnitude of the dynamic response of the rail increases as the amplitude of the irregularities increases or the wavelength decreases. In the wavelength of 2~30 m, the maximum and as the wavelength of the discontinuity sample increases, the oscillation of the power response time curve decreases significantly and tends to be smooth.

A numerical investigation is conducted to examine the mechanical properties of a novel three-dimensional (3D) isolation bearing. This device is primarily composed of a lead rubber bearing (LRB), disc springs, and U-shaped dampers. A finite element model is developed and validated against the previous experimental results. Subsequently, comprehensive analyses are performed to evaluate the influence of vertical loadings, shear strains, and the number of U-shaped dampers on the horizontal behavior, as well as the effects of displacement amplitudes and the number of dampers on the vertical performance. Under horizontal loading conditions, the bearing demonstrates reliable energy dissipation capabilities. However, the small lead core design limits its energy dissipation capacity. Compared with the bearing without U-shaped dampers, the bearing’s energy dissipation capacity increases by 628%, 1300%, and 2581% when employing 1, 2, and 4 dampers on each side, respectively. Regarding vertical performance, the innovative disc spring group design effectively reduces the tensile displacement of the LRB under tension, thereby enhancing the overall tensile capacity of the bearing. Furthermore, in comparison to their contribution to horizontal energy dissipation, the U-shaped dampers play a relatively minor role in vertical energy dissipation.