Traditional submarine tunnels with drainage systems are highly susceptible to water leakage, which is challenging to locate and manage, leading to high maintenance costs. To address this problem, a new controlled drainage system for submarine tunnels was proposed in this study. The system utilizes a double-adhesive waterproof membrane instead of traditional waterproof sheets, which not only reduces the likelihood of leakage but also makes subsequent leak detection and repair easier. In addition, replacing blind pipes with drainage sheets significantly improves the clogging resistance of the drainage system. The influence of grouting circles and drainage sheets on the water inflow and the external water pressure on the lining was then analyzed using numerical calculation methods. Finally, the design process of the new controlled drainage system was proposed. The research suggests that the new system allows for a multi-stage control method using grouting circles and drainage sheets, providing greater design flexibility. In the primary control stage, grouting circles effectively reduce the tunnel water inflow and the external water pressure on the lining, with the permeability coefficient playing a crucial role. In the secondary control stage, the spacing and width of the drainage sheets can regulate the water inflow and pressure. Unlike grouting circles, drainage sheets decrease water pressure while inevitably increasing water inflow, and vice versa. These findings can serve as a valuable reference for the design of waterproof and drainage systems in submarine tunnels.

Seismic resistance systems for small and mid-span girder bridges often lacks hierarchically repeatable earthquake resistance, leading to challenging and time-consuming post-earthquake repairs. This research introduces a novel quasi-floating seismic resistance system (QFSRS) with hierarchically sacrificial components to enable multiple instances of earthquake resistance and swift post-earthquake restoration. Finite element modeling, a numerical probabilistic approach, and earthquake-simulating shake-table tests identified highly sensitive parameters from the QFSRS to establish theoretical equations describing the mechanical model and working mechanism of the system. The results indicate that the working mechanism of the QFSRS under seismic conditions aligns with the theoretical design, featuring four hierarchically sacrificial seismic stages. Specifically, under moderate (0.3g) or higher seismic conditions, QFSRS reduced relative displacement between piers and beams by 55.15% on average. The strain at pier bases increased 6.17% across all seismic scenarios, significantly enhancing bridge seismic performance. The QFSRS provides resilient and restorable earthquake resistance for girder bridges.

A mechanical calculation model for longitudinal joints strengthened by steel ultra-high performance concrete (UHPC) composites was first proposed and validated against the numerical results. This method can continuously calculate the mechanical response of the whole process by real-time monitoring and adjusting the stress stage of each material, eliminating the need to divide stages based on experimental phenomena. Parameter analysis was performed to explored the influence of strengthening parameter and axial force level. The strengthening mechanism under sagging and hogging moments was investigated and compared. Under sagging moments, the strengthening effect is significant, boosting the load-bearing capacity by 4.14 times and increasing the flexural stiffness by 2.93 times. Under hogging moments, a more pronounced improvement in flexural stiffness is observed. For sagging moments, the primary factors influencing structural bearing capacity and stiffness are the thickness of the steel plate and UHPC, respectively. Under hogging moments, the axial force level emerged as the most critical factor for enhancing structural mechanical performance. The strengthening mechanisms differ under sagging and hogging moments, with the former effectively leveraging the mechanical properties of the strengthening material, while the latter further explore the bending resistance of the bolts. These findings contribute to the theoretical foundation for practical engineering strengthening.

The large vibrations of stay cables pose significant challenges to the structural performance and safety of cable-stayed bridges. While magnetorheological dampers (MRDs) have emerged as an effective solution for suppressing these vibrations, establishing accurate forward and inverse mapping models for MRDs to facilitate effective semi-active control of cable vibrations remains a formidable task. To address this issue, the current study proposes an innovative strategy that leverages Long Short-Term Memory (LSTM) neural networks for MRD modeling, thus enhancing semi-active control of stay cable vibrations. A high-fidelity data set accurately capturing the MRD dynamics is first generated by coupling finite element analysis and computational fluid dynamic approach. The obtained data set is then utilized for training LSTM-based forward and inverse mapping models of MRD. These LSTM models are subsequently integrated into dynamic computational models for effectively suppressing the stay cable vibrations, culminating in an innovative semi-active control strategy. The feasibility and superiority of the proposed strategy are demonstrated through comprehensive comparative analyses with existing passive, semi-active and active control methodologies involving sinusoidal load, Gaussian white noise load and rain–wind induced aerodynamic load scenarios, paving the way for novel solutions in semi-active vibration control of large-scale engineered structures.