Bridges are critical components of transportation infrastructure. To ensure the long-term performance of bridges and the safety of the public, regular inspections are required during their service. Structural performance assessments are subject to various conditions. Structural deterioration is caused by complex environmental and operational conditions (EOCs) including temperature changes, truckloads, chemical corrosion, etc. In this study, an in-site structural health monitoring (SHM) system is designed and deployed on the Caohekou Bridge in China with a series of sensors installed, providing continuous real-time data for 4 years. Crack width, vertical deformation, concrete strains, temperature, longitudinal displacement and acceleration are monitored and assessed. Time-history monitoring data are comprehensively analysed to advance our understanding of structural deterioration caused by time and temperature. It is very common to lose data during the monitoring process, especially in the long-term run. To overcome the challenge of missing data package and to realize early warning, methods including an SHM systems face, a back propagation neural network and a long short-term memory are proposed to predict the bridge responses under the change of EOCs. It has been proved that the performance of predicted crack widths is close to that of the measured value, and the trend of change is consistent. Such results indicate that approaches proposed that quantitatively assess in-service structure are promising. Therefore, effective and efficient maintenance decisions can be made to ensure an immediate response, long-term safety and serviceability of bridge structures.

The small pipe–roof–beam method has better adaptability to ultra-shallow buried subway stations. Five groups of similar model tests were carried out to explore the pipe–roof deformation, surface settlement, and beam strain caused by excavation using this method. Based on the test results, a 3D numerical model was established to study the pipe–roof deformation under different cases. The following conclusions were obtained: as the height-to-span ratio increases, the pipe–roof deformation, and surface settlement increase and, afterward, decrease. Increasing the number of beams can significantly reduce the pipe–roof deformation and surface settlement, and has a greater effect on the surface settlement. The soil-arching effect occurs above the pipe–roof during excavation, and is strengthened with an increase of height-to-span ratios. The difference between the pipe–roof deformation caused by excavation is within 2% in two cases: free at both ends and fixed at only one end. It is not recommended to add support to only one end in actual construction. Adding support at both ends can reduce the pipe–roof deformation by about 40%. The research conclusions have guiding significance for the development of the small pipe–roof–beam method. The development of subway construction has gradually become one of the themes of urban development. Finding ways to build subway stations quickly, economically, and safely has gradually become the focus of attention. The pipe–roof method is a method of constructing urban underground space, which is widely used throughout the world. However, there are many shortcomings in the existing pipe–roof method. This paper proposes the small pipe–roof–beam method that can save the construction period on the premise of ensuring safety, which is currently being applied to Shifu Road Station of Shenyang Metro Line 4 in China. In this paper, the law of surface settlement and pipe–roof deformation caused by excavation is obtained by combining the method of laboratory test and numerical simulation. The research can be the theoretical basis for the subsequent application of this method. The matching relationship between the pipe–roof and the beam will be investigated in the next study, which will provide guidance for the optimal design of subway stations.

The deformation and damage to seasonal permafrost roadbeds, as seasons shift, stems from the intricate interplay of temperature, moisture, and stress fields. Fundamentally, the frost heave and thaw-induced settlement of soil represent a multi-physics coupling phenomenon, where various physical processes interact and influence each other. In this investigation, a comprehensive co-coupling numerical simulation of both the temperature and moisture fields was successfully executed, utilizing the secondary development module within the finite element software, COMSOL Multiphysics 6.0. This simulation inverted the classical freezing–thawing experiment involving a soil column under constant temperature conditions, yielding simulation results that were in excellent agreement with the experimental outcomes, with an error of no more than 10%. Accordingly, the temperature, ice content, and liquid water content distributions within the seasonal permafrost region were derived. These parameters were then incorporated into the stress field analysis to explore the intricate coupling between the moisture and temperature fields with the displacement field. Subsequently, the frost heave and thaw settlement deformations of the roadbed were calculated, accounting for seasonal variations, thereby gaining insights into their dynamic behavior. The research results show that during the process of freezing and thawing, water migrates from the frozen zone towards the unfrozen zone, with the maximum migration amount reaching 20% of the water content, culminating in its accumulation at the interface separating the two. Following multiple freeze–thaw cycles, this study reveals that the maximum extent of freezing within the roadbed reaches 2.5 m, while the road shoulder experiences a maximum freezing depth of 2 m. A continuous trend of heightened frost heave and thaw settlement deformation of the roadbed is observed in response to temperature fluctuations, leading to the uneven deformation of the road surface. Specifically, the maximum frost heave measured was 51 mm, while the maximum thaw settlement amounted to 13 mm.