An experimental investigation on chloride diffusion in structural concrete under the cyclic impact loading is conducted. Effects of magnitudes and loading times are studied. Relationship between damage coefficients and chloride diffusion coefficients is obtained. The cyclic impact loading causes the initiation of new cracks and the propagation of existing cracks, which brings an obvious promotion for chloride diffusion. There should be a damage threshold. If the magnitude of the external loading is large enough to make the damage exceed the threshold, initiation and propagation of cracks become quite significant and chloride diffusion can be greatly promoted. With the increase of the damage coefficient, the chloride diffusion coefficient increases. The increasing rates decrease with long immersion times. Relationship curves of damage coefficients and chloride diffusion coefficients show a good correlation and can be well described with power functions.

The seismic response of underground liquefied natural gas (LNG) storage tanks has been a significant focus in both academic and engineering circles. This study utilized Ansys (2021R1) to conduct seismic analyses of large-capacity LNG tanks, considering the fluid–structure–soil coupling interaction (FSSI), and it was solved using the Volume of Fluid model (VOF) and Finite Element Method (FEM). The mechanical properties of both the LNG tank structure and soil were simulated using solid elements, and seismic acceleration loads were applied. An analysis of liquefied natural gas was performed using fluid elements within FLUENT. Initially, a modal analysis of the tank was conducted, which revealed lower frequencies for a full-liquid tank (3.193 Hz) compared to an empty tank (3.714 Hz). Subsequently, the seismic responses of both the aboveground and underground LNG tank structures were separately simulated, comparing the acceleration, stress, and displacement of the tank wall structures. The findings indicate that the peak relative displacement of the aboveground empty tank wall is 122 mm, less than that of a full tank (136 mm), while the opposite holds true for underground tanks. The period and wave height of LNG liquid shaking in underground tanks are lower than those in aboveground tanks, which is more conducive to tank safety. The deformation and acceleration of underground tanks are lower than those of aboveground tanks, but the Mises stress is higher. The results indicate that underground LNG tank structures are safer under earthquake conditions.

Ineffective methods used to detect damage in subway tunnels can result in severe safety risk. Traditional detection methods use laser scanning, image recognition, and inspection to identify damages in the inner lining of a tunnel after the subway is out of service; these methods have low efficiency and accuracy. In this study, a new method is proposed to analyze the vibration signal of a moving train based on the relative entropy of the wavelet packet energy, which can quickly identify and evaluate the damage of the subway tunnel and its auxiliary structure in real time. The test model includes a three-dimensional printed tunnel and a moving vehicle to simulate the train running in the tunnel. Wireless acceleration sensors are installed inside the vehicle and at the top of the tunnel to record the vibration signals of the car and the tunnel lining. After obtaining the acceleration signal of the vehicle, the relative entropy of energy is calculated using wavelet packet transform, in which sudden changes in entropy reflect damages. The model test results show that the vertical acceleration of the vehicle is sensitive to tunnel damage and the signal energy is mainly concentrated at 30–80 Hz and 200–400 Hz. By comparing the energy of the relative entropy between healthy and damaged signals, the location and degree of damage can be identified.

The utilization of wave energy holds significant promise as a renewable energy source, with Oscillating Water Column (OWC) Wave Energy Converters (WECs) being one of the most established technologies in this domain. This study examines the influence of various spacing configurations and different shapes of OWCs on device-device interaction, aiming to assess their impact on hydrodynamic performance. Employing a fully nonlinear 3D computational fluid dynamics (CFD) model based on RANS equations and a VOF surface capturing scheme, numerical analyses of six array cases are conducted using Star CCM+. To refine free surface wave representations, the Adaptive Mesh Refinement (AMR) technique is employed, ensuring accuracy. The model is rigorously validated against published physical measurements, encompassing chamber vertical velocity and chamber differential air pressure. After validation, a series of simulations was conducted to explore the effects of two key array layout factors: device spacing and shape, on the hydrodynamic performance. These investigations reveal significant influences on wave power and device efficiency. By providing insight into the complex dynamics between array geometries, spacing arrangements, and energy extraction, this study pushes the boundaries of wave energy conversion research, offering valuable insights for future design and implementation strategies.